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Comparison of three vision screening measures for use with primary school students 1984

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COMPARISON OF THREE VISION SCREENING MEASURES FOR USE WITH PRIMARY SCHOOL STUDENTS by JEANETTE REYNOLDS B.A., Simon F r a s e r U n i v e r s i t y , 1975 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ARTS in THE FACULTY OF GRADUATE STUDIES Department Of E d u c a t i o n a l Psychology And S p e c i a l Education We accept t h i s t h e s i s as conforming to the r e q u i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA A p r i l 1984 © Jeanette Reynolds, 1984 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of the requirements f o r an advanced degree at the U n i v e r s i t y of B r i t i s h Columbia, I agree that the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and study. I f u r t h e r agree that permission f o r e x t e n s i v e copying of t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the Head of my Department or by h i s or her r e p r e s e n t a t i v e s . I t i s understood that copying or p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l gain s h a l l not be allowed without my w r i t t e n permi s s i o n . Department of E d u c a t i o n a l Psychology And S p e c i a l Education The U n i v e r s i t y of B r i t i s h Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1W5 Date: A p r i l 18 1984 i i A b s t r a c t L i t e r a t u r e regarding the v i s i o n care needs of school c h i l d r e n i n d i c a t e s that a v a r i e t y of v i s u a l anomalies occur in s u f f i c i e n t numbers among c h i l d r e n to warrant recommendation of a comprehensive school v i s i o n s creening programme. A qua s i - e x p e r i m e n t a l study was conducted to i n v e s t i g a t e the r e f e r r a l e f f i c a c y (accuracy) of the Keystone T e l e b i n o c u l a r (KTT), the M o d i f i e d T e l e b i n o c u l a r (MTT), and the S n e l l e n a g a i n s t a standard optometric exam. S i x t y c h i l d r e n , ' aged 6-0 to 9-11, who had scheduled appointments with one of f i v e o p t o m e t r i s t s i n Coquitlam, Surrey, and White Rock, B r i t i s h Columbia, were administered the three s c r e e n i n g measures, a l e t t e r i d e n t i f i c a t i o n t e s t , and a standard optometric examination. S u b j e c t s ' performance on each sc r e e n i n g measure was compared to t h e i r performance on the standard optometric exam and c a t e g o r i z e d as a p o s i t i v e r e f e r r a l , a negative r e f e r r a l , an o v e r r e f e r r a l , or an u n d e r r e f e r r a l . Chi-square and phi c o e f f i c i e n t analyses were used to make the f o l l o w i n g comparisions: 1) the r e f e r r a l e f f i c a c y of the MTT versus that of the KTT, 2) the r e f e r r a l e f f i c a c y of the MTT versus that of the S n e l l e n , 3) the r e f e r r a l e f f i c a c y of the KTT versus that of the S n e l l e n . The MTT had grea t e r e f f i c a c y than the S n e l l e n f o r p o s i t i v e r e f e r r a l s (X2 ( 1 ) = 7 . 000 , p_<.0l) and underref e r r a l s (X 2 ( 1 )=8 . 909, p_<.0l). The S n e l l e n had grea t e r e f f i c a c y than e i t h e r the MTT (X 2 (1 ) =7 . 363 , p<.01 ) or the KTT (X 2 (1)=5 . 444, p_<.05) f o r o v e r r e f e r r a l s . O v e r r e f e r r a l s and u n d e r r e f e r r a l s were both u n d e s i r a b l e , with u n d e r r e f e r r a l s being the more s e r i o u s . In a d d i t i o n to s t a t i s t i c a l performance, the s u i t a b i l i t y of t e s t requirements f o r the t a r g e t p o p u l a t i o n and ease of a d m i n i s t r a t i o n were a l s o c o n s i d e r e d in e v a l u a t i n g the us e f u l n e s s of a scre e n i n g measure. When a l l the f a c t o r s of v i s i o n s c r e e n i n g were con s i d e r e d , the MTT proved to be the s u p e r i o r procedure f o r i d e n t i f y i n g c h i l d r e n r e q u i r i n g p r o f e s s i o n a l c a r e . i v Table of Contents A b s t r a c t i i L i s t of Tables v i i i Acknowledgement x CHAPTER I - INTRODUCTION 1 Incidence of V i s i o n D i s o r d e r s i n C h i l d r e n 1 V i s i o n and Reading 5 Purpose of the Study 7 Questions To Be Answered 8 D e f i n i t i o n of Terms 9 Screening Measures 9 KTT and MTT 9 S n e l l e n 9 Standard Optometric Exam 10 Types of R e f e r r a l s 11 P o s i t i v e R e f e r r a l s 11 Negative R e f e r r a l s 11 O v e r r e f e r r a l s 11 U n d e r r e f e r r a l s 11 CHAPTER II - LITERATURE REVIEW 12 Problems i n V i s i o n Screening 12 L i m i t a t i o n s of Screening Measures 13 V a r i a b i l i t y i n R e f e r r a l C r i t e r i a 13 Screening Personnel 16 Three Screening Measures 18 S n e l l e n L e t t e r Chart 18 V Format 1 8 Adminstration 19 Test I n t e r p r e t a t i o n 19 Avantages 21 L i m i t a t i o n s 21 Keystone T e l e b i n o c u l a r Test 27 Format and Adminstration 27 Test I n t e r p r e t a t i o n 28 Advantages 28 L i m i t a t i o n s 30 M o d i f i e d T e l e b i n o c u l a r Technique 32 Format and A d m i n i s t r a t i o n 32 Test I n t e r p r e t a t i o n 32 Advantages ; 33 L i m i t a t i o n s 33 CHAPTER III - METHOD 34 Subjects 34 Measures 36 L e t t e r I d e n t i f i c a t i o n 36 S n e l l e n 36 KTT and MTT 37 Standard Optometric Exam 38 Assumptions 38 Procedures 41 Test A d m i n i s t r a t i o n 41 Recording Data 43 Optometric Exam 44 v i Other T e s t i n g F a c t o r s 44 Sc o r i n g and I n t e r p r e t a t i o n 45 L e t t e r I d e n t i f i c a t i o n 45 S n e l l e n 45 KTT and MTT 46 Standard Optometric Exam 47 R e f e r r a l C a t e g o r i e s 47 p o s i t i v e r e f e r r a l 47 negative r e f e r r a l 47 o v e r r e f e r r a l 48 u n d e r r e f e r r a l 48 Sc o r i n g R e l i a b i l i t y 49 Data A n a l y s i s 51 D e l i m i t a t i o n s 51 CHAPTER IV - RESULTS 52 V i s u a l S k i l l s Tested 52 R e f e r r a l E f f i c a c y 54 Question 1 54 Question 2 55 Question 3 55 F i n d i n g s 55 Question 1 59 Question 2 59 Question 3 59 Comparisons f o r P o s i t i v e and Negative R e f e r r a l s 60 D i s c u s s i o n 60 S n e l l e n 63 v i i Keystone T e l e b i n o c u l a r Technique 64 M o d i f i e d T e l e b i n o c u l a r Technique 65 CHAPTER V - SUMMARY and RECOMMENDATIONS 66 Screening Measures 67 S n e l l e n 67 KTT and MTT 68 Standard Optometric Exam ' 70 Subjects and Method 70 D e l i m i t a t i o n s 72 L i m i t a t i o n s Within Measures .......72 KTT and MTT 7 3 S n e l l e n 75 R e s u l t s and Conclusions 76 Recommendations 78 Test M o d i f i c a t i o n s 78 Further Research 81 BIBLIOGRAPHY 83 APPENDIX A G l o s s a r y of V i s i o n Terms 90 APPENDIX B The M o d i f i e d C l i n i c Technique 100 APPENDIX C The Orinda Study 102 APPENDIX D Recording Forms and P r o t o c o l s ....108 APPENDIX E The CA, Sex, and Grade of Subjects 113 L i s t of Tables TABLE I Percentage of School C h i l d r e n Needing V i s i o n Care TABLE II V i s u a l S k i l l s Tested by Three Screening Measures and A Standard Optometric Exam TABLE III A m i n i s t r a t i o n Order of V i s u a l T e s t s TABLE IV Types of R e f e r r a l s TABLE V Agreement of R e f e r r a l Status on KTT and MTT p r o t o c o l s by the researcher and the independent s c o r e r ... TABLE VI Comparison and s t r e n g t h of agreement of the V i s u a l S k i l l s t e s t e d by Three Screening Measures and a Standard Optometric Exam TABLE VII Standard Score Comparisons of the Strength of Agreement between Three Screening Measures and a Standard Optometric Exam TABLE VIII Number and Percentage of S i x t y Subjects i n Each R e f e r r a l Category, per Screening Measure as Compared to a Standard Optometric Exam TABLE IX Summary of Co r r e c t and I n c o r r e c t R e f e r r a l s for Each Screening Measure as Compared to a Standard Optometric Exam TABLE X Chi-square Comparisons of the Number of R e f e r r a l s per Category between Screening Measures TABLE XI Comparison of KTT R e f e r r a l Rates f o r Primary Students i n the Present Study and i n the 1956 t e s t i n g of the Orinda Study i x TABLE XII Subjects Tested and V i s i o n T e s t s Administered Each Year d u r i n g the Orinda Study 104 TABLE XIII Keystone T e l e b i n o c u l a r Subtests Administered dur i n g the Orinda Study i n 1955 and 1956 1 05 TABLE XIV Percentage of R e f e r r a l s , by R e f e r r a l Category, i n the Orinda Study d u r i n g 1955 and 1956 106 TABLE XV Percentage of Primary Student R e f e r r a l s , by R e f e r r a l Category, in the Orinda Study d u r i n g 1955 and 1956 107 TABLE XVI Subjects by Age and Sex 114 TABLE XVII Subjects by Age and Grade 114 X Ac knowledqement I am indebted to the many individuals who co-operated, offerred advice, and provided encouragement during the course of t h i s study. In p a r t i c u l a r , I would l i k e to express my appreciation to the members of my committee: Dr. D.E. A l l i s o n , Dr. J.L. Conry, and Dr. O.A. Oldridge for the time, advice, and support they so generously gave. Invaluable suggestions and co-operation were given by the p a r t i c i p a t i n g optometrists: Drs. W.E. Jackson, J.D. Jantze, and K.M. Smith, Surrey, Dr. L.J. Mah, Coquitlam, and Dr. M.C. Sherck, • White Rock. To them my sincerest thanks. I would also l i k e to thank the B.C. Optometric Association, and in p a r t i c u l a r Mr. T.J. L i t t l e , for their support. F i n a l l y , but not lea s t , I would l i k e to thank the c h i l d r e n , and their parents, who so w i l l i n g l y agreed to p a r t i c i p a t e in the study. 1 CHAPTER I - INTRODUCTION Within d i s c i p l i n e s concerned with the w e l l - b e i n g and l e a r n i n g p o t e n t i a l of students, c u r r e n t emphasis i s on the e a r l y d e t e c t i o n of d i f f i c u l t i e s and the implementation of e a r l y i n t e r v e n t i o n s to reduce and/or r e l i e v e these d i f f i c u l t i e s . T h i s viewpoint i s supported w i t h i n the l i t e r a t u r e on v i s u a l s c r e e n i n g of school students ( E i s n e r & Oglesby, 1971; Shaw, 1964; Taubenhaus & Jackson, 1965). The issue i s not whether c h i l d r e n should undergo v i s u a l s c r e e n i n g , but what type of s c r e e n i n g would be adequate f o r school c h i l d r e n . T h i s study compared the r e l a t i v e e f f i c a c y (accuracy of r e f e r r a l s ) of the Keystone T e l e b i n o c u l a r , the M o d i f i e d T e l e b i n o c u l a r , and the S n e l l e n as v a l i d s chool v i s i o n s c r e e n i n g measures. A g l o s s a r y of s e l e c t e d v i s u a l terms i s presented i n Appendix A. Incidence of V i s i o n D i s o r d e r s in C h i l d r e n Although the l i t e r a t u r e supports the p o s i t i o n that there i s a need f o r a l l c h i l d r e n to have an e a r l y v i s u a l e v a l u a t i o n , there seems to be l i m i t e d data regarding the n a t i o n a l i n c i d e n c e of v i s i o n problems r e q u i r i n g p r o f e s s i o n a l care among c h i l d r e n i n Canada or the U n i t e d S t a t e s . A 2 report by the V i s i o n Care Task Force, B.C. M i n i s t r y of Health (1977) noted that "The p r o p o r t i o n of each age group in the p o p u l a t i o n with v i s i o n care needs i s not known" (p.112). However v a r i o u s estimates of the n a t i o n a l need f o r v i s i o n care have been made i n Canada and the Un i t e d S t a t e s . Table I shows the estimated percentage of school c h i l d r e n with v i s i o n care needs. The v a r i a b i l i t y shown i n Table I r e f l e c t s a survey of the l i t e r a t u r e on o v e r a l l i n c i d e n c e of v i s i o n needs in c h i l d r e n . The r e f e r e n c e s reported below d i s c u s s d i f f e r e n t age groups and v i s u a l anomalies thereby making comparisons d i f f i c u l t . Coleman (1970), r e p o r t i n g r e s u l t s from optometric evaluations- given to over three thousand elementary students i n West Warwick, Rhode I s l a n d , found an o v e r a l l r a t e of 15% f o r r e f r a c t i v e e r r o r s (hyeropia, myopia, and astigmatism). Hyperopia was the predominant r e f r a c t i v e e r r o r i n ki n d e r g a r t e n , grade one, and grade two. S t a r t i n g in grade three, cases of myopia began to outnumber hyperopia. In grades f i v e and s i x approximately f i v e times as many cases of myopia as hyperopia were found. However, r e f r a c t i v e e r r o r s are not the only type of v i s u a l d i f f i c u l t y experienced by c h i l d r e n . Rosen (1966) c i t e s evidence that i n d i c a t e s more than f a r p o i n t a c u i t y needs to be in c l u d e d in school v i s i o n s c r e e n i n g programmes. Of the more than s i x hundred f i r s t grade students screened i n Minneapolis, Minnesota 16.27% were reported to r e q u i r e a p r o f e s s i o n a l r e f e r r a l . S l i g h t l y more oculo-motor c o o r d i n a t i o n problems 3 (6.48%) than r e f r a c t i v e e r r o r s (4.27%) were found. Another 5.52% were found to have a combination of ocular-motor c o o r d i n a t i o n and r e f r a c t i v e problems. The O n t a r i o M i n i s t r y of H e a l t h (1976) a l s o i d e n t i f i e d two main groups of v i s i o n d e f e c t s from school v i s i o n s c r e e n i n g programmes - r e f r a c t i v e e r r o r s and strabismus. While no rate i s given for the former, the l a t t e r was r e p o r t e d to be present i n 1-2% of c h i l d r e n between f i v e and seven years. A study of 73 kin d e r g a r t e n youngsters by the School of Optometry, U n i v e r s i t y of Waterloo ( J e r v i s , 1 9 7 8 ) , found 14% of the youngsters had s e r i o u s v i s i o n handicaps and another 12% had p o t e n t i a l handicaps that r e q u i r e d p r o f e s s i o n a l m o n i t o r i n g . Incidence of v i s u a l anomalies of 20%, or g r e a t e r , have been c i t e d by Cross (1975), Harley and Lawrence (1977), and Woo and Badger (1978). While the s t a t i s t i c s of i n c i d e n c e vary they c o n s i s t e n t l y i n d i c a t e the need f o r comprehensive v i s i o n s c r e e n i n g of school aged c h i l d r e n , p a r t i c u l a r l y at the primary l e v e l . T a b l e I Percentage of School C h i l d r e n Needing V i s i o n Care age group 0-4 5-9 10-14 Boyd, 1965' 6.0 8.0 31.5 B.C. Optomet r i c A s s o c i a t i o n , 1973 12.0 18.0 Canadi an Optometr i c Assoc i at i on, 1965 2 . 5 U.S. Publ i c H e a l t h Survey, 1964, 1973 a&b 19.5 8.0 17.0 summary s t a t i s t i c s 6.0 9 .O 25 .0 Note. Summarized from P r o v i n c e of B r i t i s h Columbia (1977) 'e s t i m a t e s of Canadians needing g l a s s e s 5 V i s i o n and Reading Although debated f o r years, the exact r o l e v i s i o n p l a y s i n determining a student's success i n reading has yet to be c o n c l u s i v e l y e s t a b l i s h e d . S e v e r a l f a c t o r s l i m i t the comparison of v i s i o n s c r e e n i n g s t u d i e s : v a r i a t i o n in the age of students s t u d i e d , d i f f e r e n c e s in sampling techniques, i n v e s t i g a t i o n of d i f f e r e n t v i s i o n t e s t s , q u e s t i o n a b l e v a l i d i t y and r e l i a b i l i t y of some v i s i o n s c r e e n i n g t e s t s , d i f f e r e n c e s in the c r i t e r i a used to determine i f p r o f e s s i o n a l care was r e q u i r e d and i n d e f i n i n g reading d i s a b i l i t y , and d i f f e r e n c e s i n a n a l y z i n g data (Dreby, 1979; H a r r i s & Sipay, 1975; Rosen, 1965). R e s u l t s are a l s o i n f l u e n c e d by whether the authors are w r i t i n g from an optometric or o p h t h a l m o l o g i c a l p o i n t of view. Ophthalmologists o f t e n tend to concentrate on the p h y s i c a l mechanisms and d i s e a s e s of the eye while o p t o m e t r i s t s tend to be concerned with a broader range of f u n c t i o n a l d i s o r d e r s (e.g. f u s i o n d i f f i c u l t i e s ) . H a r r i s and Sipay (1975) suggest that r e s u l t s favour there being a p o s i t i v e r e l a t i o n -between poor near-point a c u i t y and poor eye-muscle balance and reading d i f f i c u l t i e s . From a study i n v o l v i n g 162 f i f t h grade students, Brod and Hamilton (1973) concluded that a d i s t u r b a n c e i n b i n o c u l a r v i s i o n i s s i g n i f i c a n t l y r e l a t e d to decreased reading performance. Further evidence that v i s u a l d i s o r d e r s impair mastery of reading s k i l l s i s presented by A l l e n (1977); 6 abnormal p u r s u i t and s a c c i d i c movements (see Appendix A) and abnormal focus c o n t r o l were found to be greater i n c h i l d r e n with l e a r n i n g d i s o r d e r s ( r e a d i n g ) . He a l s o maintains these d i s o r d e r s are responsive to treatment thereby p l a c i n g "...the l e a r n i n g d i s o r d e r e d c h i l d in a c o n d i t i o n of v i s u a l readiness to l e a r n to read" (p.415). Campian (1965, c i t e d in M a r t i n , 1971), claims that poor v i s u a l a c u i t y and d e f e c t s i n muscle imbalance or convergence do not d i r e c t l y i n t e r f e r e with the reading process. M a r t i n suggests that the source of a reading d i s o r d e r may l i e i n the b r a i n where v i s u a l s t i m u l i are i n t e r p r e t e d and a s s o c i a t e d with past memory and language r a t h e r than w i t h i n the eye or the o p t i c nerve. Cross (1975) c o n s i d e r s reading d i f f i c u l t i e s , i n c l u d i n g d y s l e x i a , to r e s i d e w i t h i n the c e n t r a l p r o c e s s i n g areas of the b r a i n . Bond, T i n k e r , and Wasson (1979) present a c o n c i s e summary of some c o n s i s t e n t trends found i n the l i t e r a t u r e : 1. There i s a s l i g h t l y g r e a t e r percentage of v i s u a l d e f e c t s among c h i l d r e n with reading d i s a b i l i t y than among c h i l d r e n without reading d i s a b i l i t y . 2. C h i l d r e n with v i s u a l d e f e c t s , as a group, tend to read more po o r l y than c h i l d r e n without v i s u a l d e f e c t s . 3. On the other hand, many c h i l d r e n with v i s u a l d e f e c t s l e a r n to read as w e l l as or b e t t e r than c h i l d r e n without d e f e c t s . 4. No matter what kind or type of v i s u a l d e f i c i e n c y i s s t u d i e d , some c h i l d r e n can be found who have that s p e c i f i c kind or type of v i s u a l d e f i c i e n c y and who are making good progress i n reading.(p.74) 7 In acccord with t h i s l a s t statement i s the view that good v i s i o n a i d s reading, but "problems with v i s i o n do not n e c e s s a r i l y r e s u l t i n reading problems" ( R i t t y , 1979, p.796). Dreby (1979), E b e r l y (1972), E f r o n (1965), Jobe (1976), and Rosen (1965) present s i m i l a r views. The degree to which an i n d i v i d u a l i s inconvenienced by a v i s u a l d i s o r d e r v a r i e s ; a minor d i s o r d e r may be q u i t e l i m i t i n g to one person while another may be able to compensate neuromuscularly f o r a more s e r i o u s d i s o r d e r . I t should be remembered that other p h y s i c a l c o n d i t i o n s ( i l l n e s s , f a t i g u e , m a l n u t r i t i o n ) , emotional problems, or academic d e f i c i t s may c o n t r i b u t e , alone or i n c o n j u n c t i o n with v i s u a l d i s o r d e r s , to reading d i f f i c u l t y . Thus i t may be concluded that v i s u a l d i s o r d e r s per se do not' cause reading d e f i c i t s , but may c o n t r i b u t e to a student's d i f f i c u l t y i n reading and f o r t h i s reason school s c r e e n i n g of c h i l d r e n ' s eyes i s a d v i s a b l e . Purpose of the Study The e f f i c a c y of the most commonly used school v i s i o n s c r e e n i n g procedure, the S n e l l e n l e t t e r c h a r t , has been c r i t i c i z e d by many ( H a r r i s & Sipay, 1975; Jobe, 1976; M a r s h a l l , 1969; Pennock & Shapiro, 1980; Rubin, 1972; Schubert, 1976; Spache, 1965). The purpose of t h i s study was to i n v e s t i g a t e three v i s i o n s c r e e n i n g measures for p o s s i b l e use by n o n - v i s i o n s p e c i a l i s t s i n B r i t i s h Columbia s c h o o l s . The Keystone T e l e b i n o c u l a r Technique (KTT), the 8 M o d i f i e d T e l e b i n o c u l a r Technique (MTT), as developed by Walton, and the S n e l l e n were s t u d i e d with respect to e f f i c a c y ( i . e . , accuracy) of r e f e r r a l . Student performance on these measures was compared to r e s u l t s of a r e g u l a r optometric examination. Questions To Be Answered: 1. Does the MTT have a g r e a t e r e f f i c a c y (fewer under- or o v e r r e f e r r a l s ) than the KTT when the standard optometric examination i s used as the c r i t e r i o n f o r r e f e r r a l ? 2. Does the MTT have a g r e a t e r e f f i c a c y (fewer under-or o v e r r e f e r r a l s ) than the S n e l l e n when the standard optometric examination i s used as the c r i t e r i o n f o r r e f e r r a l ? 3. Does the KTT have a g r e a t e r e f f i c a c y (fewer under- or o v e r r e f e r r a l s ) than the S n e l l e n when the standard optometric examination i s used as the c r i t e r i o n f o r r e f e r r a l ? 9 D e f i n i t i o n of Terms A b r i e f d e s c r i p t i o n of the three v i s i o n s c r e e n i n g measures i n v e s t i g a t e d and the standard optometric exam are given below. The four r e f e r r a l c a t e g o r i e s employed to d i f f e r e n t i a t e performance on each screening measure are a l s o def ined. Screening Measures Keystone T e l e b i n o c u l a r and M o d i f i e d T e l e b i n o c u l a r The Keystone T e l e b i n o c u l a r Technique (KTT) and the M o d i f i e d T e l e b i n o c u l a r Technique (MTT) are b i n o c u l a r , s t e r e o s c o p i c s c r e e n i n g instruments which employ a separate s e r i e s of cards f o r f a r and near poin t t e s t items. The eyes are t e s t e d s e p a r a t e l y and/or together on s p e c i f i c s u b t e s t s . These instruments screen f o r monocular and b i n o c u l a r a c u i t y at f a r p o i n t and reading d i s t a n c e s , muscle imbalance, f u s i o n , amblyopia, s t e r e o p i s , and c o l o u r p e r c e p t i o n . In a d d i t i o n , the MTT screens for hyperopia, astigmatism, and anisometropia. S n e l l e n Chart The S n e l l e n c h a r t c o n s i s t s of rows of d e c r e a s i n g s i z e . While both eyes l e t t e r s of remain open during t e s t i n g each i s occluded i n t u r n ; sometimes both eyes are t e s t e d t o g e t h e r . The t e s t i s administered at a d i s t a n c e of twenty feet ( s i x metres) and thus e s s e n t i a l l y measures f a r p o i n t a c u i t y and myopia, although severe hyperopia and severe astigmatism may a l s o be d e t e c t e d . Standard Optometric Examination Although the s p e c i f i c s of any c l i n i c a l exam are determined by the needs of the examinee there e x i s t s a core of measures upon which the p r o f e s s i o n a l r e l i e s as a s t a r t i n g p o i n t f o r examination. For the purposes of t h i s study a consensus was obtained from the p a r t i c i p a t i n g o p t o m e t r i s t s regarding the measures which comprise a standard optometric examination. These i n c l u d e t e s t s of o b j e c t i v e r e f r a c t i o n ( r e t i n o s c o p y ) , s u b j e c t i v e r e f r a c t i o n (myopia, hyperopia, astigmatism), t r o p i a s , p h o r i a s and f u s i o n at near and f a r p o i n t s , vergences and v e r s i o n s at f a r and near p o i n t s , amplitude of accommodation, ste r e o a c u i t y , c o l o u r v i s i o n , and i n t e r n a l and e x t e r n a l o c u l a r h e a l t h . Types of R e f e r r a l s P o s i t i v e R e f e r r a l s Those s u b j e c t s i d e n t i f i e d by a s c r e e n i n g measure as needing p r o f e s s i o n a l e v a l u a t i o n and who upon examination were pl a c e d under p r o f e s s i o n a l care ( p r e s c r i b e d c o r r e c t i v e l e n s e s , given therapy, or pl a c e d under continued o b s e r v a t i o n ) . Negative R e f e r r a l s Those s u b j e c t s f o r whom p r o f e s s i o n a l e v a l u a t i o n was not i n d i c a t e d by a s c r e e n i n g measure and who were not placed under p r o f e s s i o n a l c a r e . O v e r r e f e r r a l s ( f a l s e p o s i t i v e s ) Those s u b j e c t s i d e n t i f i e d by a s c r e e n i n g measure as needing p r o f e s s i o n a l e v a l u a t i o n , but who upon examination were not p l a c e d under p r o f e s i o n a l care ( r e f e r r e d u n n e c e s s a r i l y ) . U n d e r r e f e r r a l s ( f a l s e n e gatives) Those s u b j e c t s who should have been r e f e r r e d f o r p r o f e s s i o n a l e v a l u a t i o n as they r e q u i r e d p r o f e s s i o n a l care, but who were not. 12 CHAPTER II - LITERATURE REVIEW A v a r i e t y of procedures are a v a i l a b l e to screen v i s u a l a c u i t y , r e f r a c t i o n , muscle balance, s t e r e o p s i s , c o l o u r d i s c r i m i n a t i o n , or a combination of these. Examples i n c l u d e : the S n e l l e n l e t t e r c h a r t , I l l i t e r a t e E t e s t , A l l e n cards, HOVT, Ortho-Rater, Keystone T e l e b i n o c u l a r , Titmus S t e r e o t e s t , Maddox rod t e s t , and the Cover T e s t . In keeping with the o b j e c t i v e to compare three s c r e e n i n g instruments with the standard optometric examination t h i s review i s c o n f i n e d to s t u d i e s concerning the S n e l l e n c h a r t , the Keystone T e l e b i n o c u l a r Test, and the M o d i f i e d T e l e b i n o c u l a r Technique. No attempt i s being made to provide a g e n e r a l i z e d or comprehensive account of v i s i o n s c r e e n i n g techn iques. Problems in -Vision Screening P r i o r to d i s c u s s i n g the three t e s t s s e l e c t e d f o r i n v e s t i g a t i o n some c o n s i d e r a t i o n s a p p l i c a b l e to any v i s i o n s c r e e n i n g programme are presented. 1 3 L i m i t a t i o n s of Screening Measures Of paramount importance in the use of any t e s t i s r e c o g n i t i o n of both i t s advantages and l i m i t a t i o n s ; techniques of v i s i o n s c r e e n i n g are no e x c e p t i o n . R e s u l t s obtained from a v i s i o n s c r e e n i n g programme, whether a s i n g l e technique or a b a t t e r y of t e s t s , are not e q u i v a l e n t to those from a c l i n i c a l examination. Screening r e s u l t s do not equal d i a g n o s i s . The l a t t e r can only be made by ophth a l m o l o g i s t s or o p t o m e t r i s t s , not sc r e e n i n g personnel (Bond et a l . , 1979; H a r r i s & Sipay, 1975; Jobe, 1976; O n t a r i o M i n i s t r y of Health, 1976; Spache, 1965). Therefore, the purpose of a school v i s i o n s creening programme i s to i d e n t i f y those students who r e q u i r e p r o f e s s i o n a l - a t t e n t i o n , be that examination only, examination p l u s treatment, or examination with continued o b s e r v a t i o n , r a t h e r than to diagnose v i s u a l problems or t h e i r causes. V a r i a b i l i t y i n R e f e r r a l C r i t e r i a Acknowledgement of the fundamental d i f f e r e n c e s between s c r e e n i n g t e s t s , c l i n i c a l examination, and d i a g n o s i s p a r t l y accounts f o r the apparent d i s c r e p a n c i e s between scr e e n i n g r e f e r r a l s and in c i d e n c e of v i s i o n problems' based on c l i n i c a l treatment. Given that the purpose of scr e e n i n g measures i s to i d e n t i f y i n d i v i d u a l s i n need of p r o f e s s i o n a l r e f e r r a l they should only be i n t e r p r e t e d as pass or f a i l . Agreement 1 4 regarding the passing c r i t e r i a does not e x i s t e i t h e r among t e s t s or among v i s i o n care s p e c i a l i s t s . T h i s lack of accord r e s u l t s i n disagreement as to the number of c h i l d r e n who are c o r r e c t l y r e f e r r e d , those who are r e f e r r e d u n n e c e s s a r i l y ( o v e r r e f e r r a l s ) , and those the sc r e e n i n g techniques do not r e f e r , but should ( u n d e r r e f e r r a l s ) . Another f a c t o r c o m p l i c a t i n g the c l a s s i f i c a t i o n of r e f e r r a l s r a i s e d by Jobe (1976) i s that v i s i o n problems needn't be synonymous with v i s i o n d e f e c t s , but ra t h e r a student's v i s i o n "...may not be adequate f o r the tasks he i s expected to perform" (p.3). The concern with f u n c t i o n r e f l e c t s not only the c o n t r o v e r s y surrounding passing c r i t e r i a , but a l s o the d i f f e r r i n g , and at times opposing, o r i e n t a t i o n s of op h t h a l m o l o g i s t s and o p t o m e t r i s t s . • Within the l i t e r a t u r e i t i s suggested that agreement regarding p a s s i n g c r i t e r i a between those r e s p o n s i b l e for conducting the v i s i o n s c r e e n i n g and the l o c a l s p e c i a l i s t s who w i l l r e c e i v e the r e f e r r a l s i s more important than f o l l o w i n g a r b i t r a r y c r i t e r i a (Blum, Pete r s , & Bettman, 1959; E i s n e r & Oglesby, 1971; R i t t y , 1979; Rosen, 1969) While s t a n d a r d i z e d c r i t e r i a have yet to be adopted the f o l l o w i n g c u t - o f f s have been suggested as i n d i c a t i v e of the need f o r p r o f e s s i o n a l e v a l u a t i o n . They r e f l e c t the d i v e r s i t y of c r i t e r i a between scr e e n i n g procedures and repor t e d s t u d i e s . The O n t a r i o M i n i s t r y of Hea l t h (1976) a d v i s e d r e f e r r a l 1 5 i f v i s u a l a c u i t y of preschool or school aged c h i l d r e n was poorer than 20/30 i n e i t h e r eye. The N a t i o n a l S o c i e t y for Prevention of B l i n d n e s s (1969, in Harley & Lawrence, 1977) recommended a c u i t y l e v e l s allow for changes i n v i s i o n with maturation: 20/50 or poorer f o r three year o l d s , 20/40 or poorer for ages four through e i g h t , and 20/30 or poorer f o r students above the t h i r d grade. Muscle balance should be screened using the Maddox rod t e s t with r e f e r r a l s f o r l a t e r a l d e v i a t i o n s of four prism d i o p t e r s (see Appendix A) at twenty f e e t , e i g h t prism d i o p t e r s at near p o i n t , inward d e v i a t i o n s of s i x d i o p t e r s at fa r or near p o i n t , and v e r t i c a l imbalance of more than one d i o p t e r . The c l i n i c a l c r i t e r i a employed in the Orinda study (Blum et a l . , 1959), (see Appendix C), and recommended by Jobe (1976) were: v i s u a l a c u i t y of 20/40 or l e s s , r e f r a c t i v e e r r o r s - hyperopia +1.50 D.S. or more, myopia -0.50 D.S. or more, astigmatism ±1.00 D.S. or more, and amisometropia when there i s a d i f f e r e n c e of 1 between eyes; c o o r d i n a t i o n at f a r p o i n t - any t r o p i a , inward or outward movement of f i v e d i o p t e r s or more, v e r t i c a l imbalance of two or more d i o p t e r s ; c o o r d i n a t i o n at near p o i n t - any t r o p i a , inward movement of s i x plus d i o p t e r s , outward t u r n i n g of ten or more d i o p t e r s , upward t u r n i n g of two d i o p t e r s or more; any known organic anomaly. Another method of i n t e r p r e t i n g a c h i l d ' s performance on 1 6 e i t h e r s c r e e n i n g or c l i n i c a l t e s t s i s to focus on what d i f f e r e n c e , i f any, i s d i s p l a y e d between the r e l a t i v e f u n c t i o n i n g of the eyes. Screening Personnel Screening personnel are a determining f a c t o r in the scope and accuracy of any school v i s i o n s c r e e n i n g programme. I d e a l l y , every c h i l d would have a f u l l c l i n i c a l e v a l u a t i o n p r i o r to or soon a f t e r e n t e r i n g s c h o o l , with p e r i o d i c checks du r i n g h i s / h e r school y e a r s . At present t h i s i d e a l i s not f e a s i b l e in terms of p r o f e s s i o n a l manpower or economics. Nor i s i t l i k e l y every parent would assume t h i s r e s p o n s i b i l i t y . R e s u l t s from the Orinda study (Blum et a l . , 1959) (see Appendix C) showed the M o d i f i e d C l i n i c Technique (see Appendix B), which c l o s e l y approximated a c l i n i c a l e v a l u a t i o n , to be the most accurate school v i s i o n s creening programme. Although d e s i r a b l e , t h i s technique i s i m p r a c t i c a l f o r many school d i s t r i c t s because of the need f o r o p h t h a l m o l o g i s t s or o p t o m e t r i s t s to conduct the screen i n g . To meet the d e s i r e d goal of a d i s t r i c t wide scr e e n i n g programme, many d i s t r i c t s have adopted procedures which r e l y on p u b l i c h e a l t h nurses, school nurses, or teachers t r a i n e d i n the procedure employed and o f t e n a s s i s t e d by t r a i n e d v o l u n t e e r s . The emphasis i s being put on t r a i n e d personnel 1 7 rather than any p a r t i c u l a r s c r e e n i n g t e s t or combination of t e s t s (Ontario M i n i s t r y of Health, 1976). Taubenhaus and Jackson (1969) support the view that accurate v i s i o n s c reening may be done by n o n - v i s i o n s p e c i a l i s t s . In t h e i r p r e school v i s i o n s c r e e n i n g study they found that community v o l u n t e e r s who were a l e r t , i n t e l l i g e n t , and possessed empathy for c h i l d r e n c o u l d be t r a i n e d as s a t i s f a c t o r y s c r e e n e r s . U n t i l such time as v i s i o n care i s r e a d i l y a v a i l a b l e throughout the p r o v i n c e , one p o s s i b l e means of o b t a i n i n g thorough v i s i o n s c r e e n i n g for students i n B r i t i s h Columbia would be for l e a r n i n g a s s i s t a n t t e a c h e r s , school p s y c h o l o g i s t s , and school nurses to be t r a i n e d in a comprehensive screening procedure. Besides t r a i n i n g , the i n t e r e s t of the examiner towards both c h i l d r e n and the s c r e e n i n g programme a f f e c t s the accuracy of r e f e r r a l s . T h i s f a c t o r became evident i n the use of the Keystone T e l e b i n o c u l a r Test in the Orinda study (Blum et a l . , 1959). I n v e s t i g a t i o n i n t o the numerous o v e r r e f e r r a l s from the T e l e b i n o c u l a r in 1955 r e v e a l e d that the i n d i v i d u a l assigned to t h i s procedure, while adequately t r a i n e d , lacked i n t e r e s t i n the programme and only r e l u c t a n t l y accepted the job. Among the changes i n s t i t u t e d the f o l l o w i n g year was the employment of i n t e r e s t e d s c r e e n e r s ; more e f f i c i e n t r e s u l t s (fewer unnecessary r e f e r r a l s ) were then obtained. 18 Three Screening Measures The three v i s i o n s c r e e n i n g measures i n v e s t i g a t e d i n t h i s study were the S n e l l e n , the Keystone T e l e b i n o c u l a r (KTT), and the M o d i f i e d T e l e b i n o c u l a r (MTT). A d e s c r i p t i o n i s given f o r each t e s t along with i t s advantages and l i m i t a t i o n s . Test i n t e r p r e t a t i o n i s a l s o d i s c u s s e d f o r each sc r e e n i n g measure. S n e l l e n L e t t e r Chart Format An o f t e n used instrument to screen c h i l d r e n ' s v i s i o n i s the S n e l l e n l e t t e r c h a r t developed, in 1862, by the Dutch ophthalmologist Hermann S n e l l e n . The design of S n e l l e n ' s c h a r t was based on Frans Donders' work in geometric o p t i c s . For the i n i t i a l c h a r t S n e l l e n chose the l e t t e r E because of the s i m p l i c i t y of i t s form. The s i z e of each l e t t e r and the spacing between rows on the c h a r t were c a l c u l a t e d from the v i s u a l angle of f i v e minutes of an arc at v a r y i n g d i s t a n c e s . Today t h i s E c h a r t i s known as the I l l i t e r a t e E or Tumbling E t e s t and i s used p r i m a r i l y with p r e s c h o o l e r s and non- readers. The S n e l l e n t e s t used to screen o l d e r students i s 19 a c h a r t having a random assortment of l e t t e r s , but designed in the same way as the o r i g i n a l E c h a r t . Admini s t r a t ion The t e s t i s a d m i n i s t e r e d using e i t h e r a w a l l chart and the a v a i l a b l e room l i g h t i n g or by a c h a r t stand with an i n t e r n a l l i g h t source. Students may s i t or stand twenty f e e t ( s i x metres) from the c h a r t . The eyes are t e s t e d s e p a r a t e l y , an o c c l u d e r being p l a c e d over each eye in t u r n . Students are i n s t r u c t e d to keep both eyes open during s c r e e n i n g . Although the s t a n d a r d i z e d a d m i n i s t r a t i o n procedure of the N a t i o n a l S o c i e t y f o r the Prevention of B l i n d n e s s (Harley and Lawrence, 1977) recommends both eyes f i r s t be t e s t e d together, the l i t e r a t u r e surveyed i m p l i e s t h i s recommendation i s seldom f o l l o w e d . Test I n t e r p r e t a t i o n An i n d i v i d u a l ' s v i s u a l a c u i t y i s noted by the S n e l l e n f r a c t i o n where the "...denominator i n d i c a t e s the s m a l l e s t l e t t e r s or symbols seen, and the numerator i n d i c a t e s the t e s t d i s t a n c e . The l a r g e r the denominator the worse the a c u i t y " ( B r a j k o v i c h , 1980, p.473). For example a person whose v i s u a l a c u i t y i s 20/100 would read at 20 f e e t the l e t t e r s a person with "normal" v i s i o n (20/20) would see at 20 100 f e e t . Although 20/20 (6/6 using the metric s c a l e ) i s commonly r e f e r r e d to as normal v i s i o n t h i s term i s a misnomer. Many i n d i v i d u a l s have b e t t e r than 20/20 a c u i t y (e.g. 20/15 or 20/10) and 20/30 or 20/40 a c u i t y in young c h i l d r e n r e f l e c t s t h e i r developmental l e v e l r a t her than a v i s i o n d i s o r d e r . Instead von Noorden (1980) a d v i s e s the term standard v i s i o n be used. Harley and Lawrence (1977), Jobe (1976), M a r s h a l l (1969), and V e t t e r l i (1959) support t h i s p o s i t i o n . The twenty foot measure i s u s e f u l f o r d i a g n o s i s because at t h i s d i s t a n c e l i g h t rays are so n e a r l y p a r a l l e l that the eyes are able to c l e a r l y focus the stimulus on the r e t i n a while remaining at r e s t (without accommodation). T h e r e f o r e , e r r o r s on the 20/20 l i n e suggest the eyes are having to accommodate to focus the stimulus c l e a r l y . No e r r o r s imply the person sees what s/he ought to see at twenty f e e t . S n e l l e n f r a c t i o n s are a means of e x p r e s s i n g v i s u a l a c u i t y . They do not represent a percentage of v i s i o n ; 20/40 a c u i t y does not represent 50% poorer v i s i o n than 20/20 a c u i t y . "In the AMA [ American Medical A s s o c i a t i o n ] s c a l e of v i s u a l e f f i c i e n c y , 20/40 would be 15% r e d u c t i o n from 'normality', hence 85%" (Rubin, 1972, p.31). The S n e l l e n c h a r t i s a measure of d i s t a n t c e n t r a l f i e l d a c u i t y . I t was designed as a s c r e e n i n g device of the v i s u a l pathways and r e f r a c t i o n and hence r e s u l t s should not be i n t e r p r e t e d d i a g n o s t i c a l l y . B r a j k o v i c h (1980) presented the 21 f o l l o w i n g g u i d e l i n e s f o r i n t e r p r e t i n g the S n e l l e n : When the t e s t i s normal, i t should i n d i c a t e the f o l l o w i n g ; (1) that myopia i s not present or, i f present, i s of a minor degree or has been compensated; (2) that hyperopia, i f present, has been compensated by accommodation; (3) that the cornea and lens are c l e a r and permit an image to be formed on the r e t i n a ; (4) that the fovea c e n t r a l i s [ an area of the r e t i n a ] i s i n t a c t as w e l l as nervous connections to the b r a i n ; (5) that p e r c e p t i o n by the higher v i s u a l c e n t e r s i s intact.(p.473-4) Advantages The S n e l l e n ' s low c o s t , ease of a d m i n i s t r a t i o n and short a d m i n i s t r a t i o n time per examinee have c o n t r i b u t e d to i t s worldwide usage. I t i s one of the most common v i s u a l s c r e e n i n g instruments used in today's sc h o o l s ; 67% of the respondents i n Pennock and Shapiro's (1980) survey i n d i c a t e d use of t h i s c h a r t . Proponents of the t e s t maintain a l a r g e number of c h i l d r e n with v i s i o n problems, p a r t i c u l a r l y myopia, are d e t e c t e d . Rubin (1972) c o n s i d e r s the S n e l l e n to be the best a v a i l a b l e measure of a l l - a r o u n d seeing a b i l i t y . L i m i t a t ions The S n e l l e n i s s e v e r e l y c r i t i c i z e d in the l i t e r a t u r e on the b a s i s of procedure, content, and desig n . ( H a r r i s & Sipay, 1975; Jobe, 1976; M a r s h a l l , 1969; Rubin, 1972; 22 Schubert, 1976; Spache,1965). Standardized t e s t i n g c o n d i t i o n s and a d m i n i s t r a t i o n procedures are requirements of any t e s t . The S n e l l e n ' s format makes i t vunerable on both these accounts. Use of a wa l l c h a r t and the a v a i l a b l e room l i g h t i n g does not ensure adequate or c o n s i s t e n t i l l u m i n a t i o n from one- a d m i n i s t r a t i o n to the next. Nor w i l l room l i g h t i n g and the b u i l t i n l i g h t i n g of the cha r t stand n e c e s s a r i l y be e q u i v a l e n t . I n c o n s i s t e n c y may a l s o occur i n the d i s t a n c e between students and the c h a r t . V a r i a t i o n s among c h a r t s produced by d i f f e r e n t manufacturers a l s o c o n t r i b u t e to r e f e r r a l d i s c r e p a n c i e s among p a t i e n t s and f o r students t e s t e d at d i f f e r e n t times with d i f f e r e n t c h a r t s . Often other students are w a i t i n g in the t e s t i n g room while one i s being screened and thus have the o p p o r t u n i t y to memorize the cha r t before t h e i r t u r n . Some youngsters may c l o s e the eye covered by the oc c l u d e r or they may squ i n t thereby d i s t o r t i n g t e s t accuracy. von Noorden (1980) p o i n t s out that although the reason i s u n c e r t a i n , b i n o c u l a r v i s u a l a c u i t y i s b e t t e r than monocular v i s u a l a c u i t y . The i m p l i c a t i o n seems to be that t e s t s l i k e the S n e l l e n are of l i m i t e d value i n determining a person's v i s u a l s t a t u s . I n t e r - s c r e e n e r d i f f e r e n c e s i n a d m i n i s t r a t i o n and i n t e r p r e t a t i o n are another l i m i t a t i o n . Some screeners maintain i t i s necessary to begin with the l a r g e s t l e t t e r s and s y s t e m a t i c a l l y progress through the rows u n t i l a l l 23 l e t t e r s i n one row are i n c o r r e c t l y i d e n t i f i e d . Jobe (1976) proposes i t i s s u f f i c i e n t to begin with the l a r g e s t l e t t e r (20/200) to acquaint the student with the procedure, then to present the 20/50 l i n e and i f no e r r o r s are made to go to the 20/20 l i n e , only i f passin g c r i t e r i o n i s not met i s the 20/30 l i n e presented. Controversy e x i s t s as to the ap p r o p r i a t e p a s s i n g c r i t e r i o n . Some screeners c o n s i d e r a l i n e passed i f four of the s i x items are c o r r e c t l y i d e n t i f i e d , while others r e q u i r e a l l s i x to be c o r r e c t . Whether the 20/20, 20/30, or 20/40 l i n e serves as the r e f e r r a l c r i t e r i o n i s a l s o debated. Some consensus i s present to recommend the 20/30 l i n e as the r e f e r r a l standard, e s p e c i a l l y f o r students beyond the primary grades; that i s , a student making e r r o r s on t h i s l i n e would be r e f e r r e d f o r c l i n i c a l examination (Blackhurst & Radke, 1964; N a t i o n a l S o c i e t y f o r the Prevention of B l i n d n e s s , 1969, i n Harley & Lawrence, 1977; O n t a r i o M i n i s t r y of Hea l t h , 1976). As noted e a r l i e r the s e l e c t i o n of a c r i t e r i o n should be made j o i n t l y between scr e e n i n g personnel and l o c a l v i s i o n s p e c i a l i s t s . One of the main l i m i t a t i o n s of the S n e l l e n i s i t s r e s t r i c t e d content. I t i s a t e s t of monocular d i s t a n c e v i s u a l a c u i t y which d e t e c t s myopia, amblyopia, and severe hyperopia and astigmatism. The f o l l o w i n g are not de t e c t e d : near p o i n t or reading a c u i t y ( u nless an a l t e r n a t e form i s given at s i x t e e n i n c h e s ) , moderate degrees of hyperopia which a student can overcome by accommodation during the 24 b r i e f s c r e e n i n g p e r i o d , b i n o c u l a r c o o r d i n a t i o n , f u s i o n , most astigmatism, f i x a t i o n , convergence, s t e r e o p s i s , and c o l o u r v i s i o n . Design c h a r a c t e r i s t i c s have l e d to c h a l l e n g e s a g a i n s t the S n e l l e n ' s v a l i d i t y . Spache (1965) s t a t e s that "...the l e t t e r s of the alphabet or the E's used are not dependable, accurate measures of a c u i t y " (p.43). He f u r t h e r claims "Some of the l i n e s are e a s i e r to read than o t h e r s , while some are e s p e c i a l l y d i f f i c u l t because of the s i m i l a r i t y of the l e t t e r s . " Data are not c i t e d to support these c l a i m s . More s p e c i f i c c r i t i c i s m s are o f f e r e d by Rubin (1972): there i s an i r r e g u l a r p r o g r e s s i o n in l e t t e r s i z e s between l i n e s , l a c k of c o n s i s t e n c y in the space, s e p a r a t i n g l e t t e r s i n a given l i n e , and non-standard spacing between l i n e s . The spacing used in a p a r t i c u l a r c h a r t may c r e a t e a "crowding phenomenon" (p.32) which c o u l d i n f l u e n c e the examinee's t e s t performance. He a l s o d i s p u t e s that the l e t t e r s comprising the S n e l l e n c h a r t c o n s t i t u t e a measure of a c u i t y , s p e c i f i c a l l y r e s o l u t i o n a c u i t y and that r e s o l u t i o n a c u i t y i s an index of general v i s u a l a b i l i t y . 25 Very few, indeed, of the l e t t e r s on a S n e l l e n c h a r t c o n s t i t u t e r e s o l u t i o n t a r g e t s at a l l . The L does not, nor does the T, D, A, 0 (unless i t i s compared with the C), P (unless i t i s compared d i r e c t l y with the F ) , .... A c h a r t comprising only B's and E's, or one bearing only F's and P's or only O's and C's, c o u l d be a very f i n e primary a c u i t y c h a r t , but one might then j u s t as w e l l use Landolt r i n g s [see Appendix A] with v a r i o u s o r i e n t a t i o n s and be done with i t . (p.30) Pe r c e p t i o n more than r e s o l u t i o n i s i n v o l v e d i n i d e n t i f y i n g l e t t e r s on the S n e l l e n , the t e s t t h e r e f o r e being a measure of a student's l e t t e r shape r e c o g n i t i o n . But he contends "The v a r i o u s l e t t e r s ... are not equal as t e s t s of v i s i b i l i t y or shape r e c o g n i t i o n . A few measure r e s o l u t i o n or r e s o l u t i o n and one or more a d d i t i o n a l f u n c t i o n s . The c h a r t as a whole, then, measures an i n e x t r i c a b l e complex of v i s u a l f u n c t i o n s - not ' v i s u a l a c u i t y ' " (Rubin,1972, p.30). T h e r e f o r e , i n c o n t r a s t to many re s e a r c h e r s and v i s i o n p e r s o n n e l , Rubin advocates the S n e l l e n c h a r t be used to screen general seeing a b i l i t y , but not a c u i t y . E f f i c a c y of r e f e r r a l i s an important f a c t o r when s e l e c t i n g a v i s i o n s c r e e n i n g programme. The debate over what c o n s t i t u t e s a c o r r e c t r e f e r r a l has been p r e v i o u s l y d i s c u s s e d . Some res e a r c h e r s have been concerned with the o v e r r e f e r r a l r a t e s of techniques while others have pressed f o r c o n s i d e r a t i o n of both over- and u n d e r r e f e r r a l s . C o n f l i c t i n g r e p o r t s e x i s t r e g a r d i n g the S n e l l e n ' s r e f e r r a l e f f i c a c y . B r a j k o v i c h (1980) suggests 97% of the c h i l d r e n 26 with s i g n i f i c a n t v i s i o n problems w i l l be i d e n t i f i e d . In c o n t r a s t , Spache (1965) claims only 20% to 40% of students r e q u i r i n g p r o f e s s i o n a l a t t e n t i o n w i l l be d i s c o v e r e d . He -reports the S n e l l e n ' s u n d e r r e f e r r a l r a t e , based on the 1949 St. Louis study, to be 25%. The d i f f i c u l t y i n v o l v e d in i n t e r p r e t i n g r e s e a r c h f i n d i n g s and choosing a s c r e e n i n g technique i s evident i n the r e f e r r a l r a t e s presented by E i s n e r and Oglesby (1971): o v e r r e f e r r a l s f o r the S n e l l e n ranged from 32.7% to 35.4% with u n d e r r e f e r r a l s of 16.4% to 51.3%. Despite the t e s t ' s advantages in terms of low cost and ease of a d m i n i s t r a t i o n , i t s numerous l i m i t a t i o n s have prompted development of more comprehensive s t a n d a r d i z e d v i s i o n s c r e e n i n g b a t t e r i e s . Two such b a t t e r i e s , the Keystone T e l e b i n o c u l a r Test and the M o d i f i e d T e l e b i n o c u l a r Technique, were employed in the present study. 27 Keystone T e l e b i n o c u l a r Test Format and A d m i n i s t r a t i o n The Keystone T e l e b i n o c u l a r Test (KTT), a l s o known as the Keystone School Survey, was developed in 1934 by E.A. B e t t s as a v i s u a l reading readiness t e s t (Harley & Lawrence, 1977). I t i s a b i n o c u l a r , s t e r e o s c o p i c s c r e e n i n g instrument c o n s i s t i n g of two s i d e - b y - s i d e achromatic prism lenses separated by an i n t e r l e n s o c c l u d e r which r e s t r i c t s the v i s i o n f i e l d of each eye, thereby c o n t r o l l i n g the stimulus to each eye. Test p l a t e s are p l a c e d in a c a r d holder s i t u a t e d at s p e c i f i c d i s t a n c e s from the l e n s e s . Far p o i n t (20 f e e t or 6 metres) and near poin t (reading d i s t a n c e of 16 inches or 41 cm) are produced o p t i c a l l y and t h e r e f o r e are s t a n d a r d i z e d between a d m i n i s t r a t i o n s . Test p l a t e images d i f f e r s l i g h t l y f o r each eye, thus s i m u l a t i n g a c t u a l scenes viewed by the examinee's eyes. The t e s t measures monocular and b i n o c u l a r d i s t a n c e and near poin t a c u i t y , h o r i z o n t a l and v e r t i c a l eye-muscle balance, f a r and near poin t f u s i o n , s t e r e o p s i s (depth p e r c e p t i o n ) , and c o l o u r v i s i o n . A v a i l a b l e supplementary m a t e r i a l s i n c l u d e a primary s k i l l s t e s t set (recommended f o r students below grade t h r e e ) , a p l u s lens t e s t to check for hyperopia, and a periometer t e s t of s i d e v i s i o n . The l i t e r a t u r e surveyed d i d not i n d i c a t e that any of these 28 supplementary t e s t s are r o u t i n e l y i n c l u d e d i n v i s i o n s c reening programmes employing the KTT. The Keystone T e l e b i n o c u l a r i s s i m i l a r to the Ortho- Rater and the Titmus School V i s i o n T e s t e r . Test I n t e r p r e t a t i o n Designed s o l e l y as a v i s i o n s c r e e n i n g procedure, the KTT must be i n t e r p r e t e d as a whole. Subtest performance does not y i e l d d i a g n o s t i c data, t h e r e f o r e r e s u l t s should not be compared to f i n d i n g s from c l i n i c a l t e s t s of the same name. The purpose of the KTT, as with any v i s i o n s creening programme, i s to i d e n t i f y students i n need of p r o f e s s i o n a l evaluat i o n . R e f e r r a l c r i t e r i a are presented in the t e s t manual to guide the examiner i n e v a l u a t i n g examinee performance. In a d d i t i o n , t y p i c a l examinee responses, for each su b t e s t , f a l l i n t o one of three c a t e g o r i e s i n d i c a t e d on the r e c o r d form: expected response, r e - t e s t area, or u n s a t i s f a c t o r y . Advantages Several advantages recommend the KTT over the S n e l l e n c h a r t . Besides screening a v a r i e t y of s k i l l s , the KTT has both a s t a n d a r d i z e d sequence of t e s t s and a d m i n i s t r a t i v e 29 procedure. A d m i n i s t r a t i v e c o n s i s t e n c y i s a l s o a i d e d by the t e s t p l a t e s which c o n t r o l the stimulus presented to each eye and the viewing d i s t a n c e . An i n t e r n a l l i g h t source provides s t a n d a r d i z e d , constant i l l u m i n a t i o n . Occluders a t t a c h e d to the instrument permit s t a n d a r d i z e d monocular a c u i t y t e s t i n g . The instrument i s p o r t a b l e , r e q u i r e s l i t t l e t a b l e space, and can be a d j u s t e d f o r v a r y i n g h e i g h t s . Another a t t r a c t i v e f e a t u r e of t h i s technique i s that i t can be administered by n o n - v i s i o n p r o f e s s i o n a l s a f t e r b r i e f t r a i n i n g . Record forms are e a s i l y completed and i n c l u d e student i d e n t i f i c a t i o n data, space for r e c o r d i n g r a p i d s c r e e n i n g and comprehensive t e s t b a t t e r y r e s u l t s , p l u s the s t a n d a r d i z e d questions f o r the comprehensive b a t t e r y . T y p i c a l examinee responses are recorded under three performance c a t e g o r i e s which reduces s u b j e c t i v e response e v a l u a t i o n by the examiner. Thus passin g c r i t e r i a are more s t a n d a r d i z e d than on the S n e l l e n where examiner pr e f e r e n c e s e t s p a s s i n g at four of s i x or s i x of s i x c o r r e c t responses. The c o n c i s e l y w r i t t e n manual d e t a i l s instrument components, t e s t a d m i n i s t r a t i o n , and the i n d i v i d u a l s u b t e s t s of the r a p i d s c r e e n i n g t e s t , the comprehensive b a t t e r y , the primary s k i l l s t e s t (which may be given to primary students r a t h e r than the comprehensive b a t t e r y ) , t h e p l u s lens t e s t , and the periometer t e s t . Passing c r i t e r i a f o r most subt e s t s are suggested, along with the p o s s i b l e i m p l i c a t i o n of i n c o r r e c t responses. 30 L i m i t a t i o n s Fewer disadvantages have been repo r t e d f o r the KTT than for the S n e l l e n . Jobe (1976) r a i s e s the concern that the occluder between the lenses might be too wide for some primary students. In the attempt to see through both lenses a youngster would s h i f t h i s / h e r head from s i d e to side d i s t o r t i n g t e s t accuracy. A p o t e n t i a l d e t e r r e n t to a school d i s t r i c t ' s adopting use of the KTT i s i t s c o s t ; approximately s i x hundred and s i x t y - f i v e d o l l a r s , U.S. funds, i n February 1981. The t e s t ' s advantages c o u l d be c o n s i d e r e d to o f f s e t the high i n i t i a l o u t l a y . The r e f e r r a l e f f i c a c y of the KTT i s c o n t r o v e r s i a l . Harley and Lawrence (1977, c i t i n g Foote & Crane, 1954) and Wi l l i a m s (1974) maintain the t e s t has a high o v e r r e f e r r a l r a t e which l i m i t s i t s s u i t a b i l i t y as a school v i s i o n s c r e e n i n g programme. H a r r i s and Sipay (1975) and Mangrum (1970), on the other hand, support school use of the KTT. Mangrum f e e l s the technique checks the major v i s i o n problems common i n c h i l d r e n with reading d i f f i c u l t i e s . R e s u l t s from the 1956 t e s t i n g conducted as part of the Orinda study (Blum et a l . , 1959) i n d i c a t e d the KTT to be a u s e f u l school v i s i o n s c r e e n i n g technique: 9% c o r r e c t r e f e r r a l s , 6% o v e r r e f e r r a l s , 8% u n d e r r e f e r r a l s , and 77% n o n - r e f e r r a l s . Thus the v i s u a l s t a t u s of 86% of the s u b j e c t s ( c o r r e c t r e f e r r a l s p l u s non- r e f e r r a l s ) was c o r r e c t l y i d e n t i f i e d , while that of 14% ( o v e r r e f e r r a l s and u n d e r r e f e r r a l s ) was erroneously 31 c l a s s i f i e d . T e c h n i c a l data are l a c k i n g f o r the KTT. Apart from S n e l l e n e q u i v a l e n t s f o r monocular d i s t a n c e and near a c u i t y , a v a i l a b l e i n the manual, no t e c h n i c a l standards are p r o v i d e d . No r e f e r e n c e i s provided f o r the S n e l l e n e q u i v a l e n t s , t h e r e f o r e i t c o u l d not be a s c e r t a i n e d whether these c r i t e r i a are in accord with those set by Canadian or American Medical A s s o c i a t i o n s . Data on which passing c r i t e r i a were based i s not presented p r e v e n t i n g comparision of KTT r e f e r r a l c r i t e r i a with those of other techniques. Nor are data provided on the r e l i a b i l i t y or v a l i d i t y of the KTT. The manual s t a t e s the procedure to be "...accurate and dependable....Overall r e s u l t s show very high v a l i d i t y . In f a c t , the t e s t s are so r e l i a b l e that thousands of eye s p e c i a l i s t s use them to a s s i s t in t h e i r diagnoses. And the t e s t s are accepted and approved by l e a d i n g p r o f e s s i o n a l o r g a n i z a t i o n s . " Data supporting these c l a i m s are l a c k i n g . None of the l i t e r a t u r e s u p p l i e d by the manufacturer i n d i c a t e d the a v a i l a b i l i t y of a t e c h n i c a l manual. J u s t i f i c a t i o n f o r the s u b s t i t u t i o n of the primary s k i l l s t e s t s , f o r the comprehensive b a t t e r y , u n t i l the end of the second grade rather than the f i r s t grade, i s not g i v e n . The equivalency of the primary and comprehensive forms can only be assumed, as supporting data are missing from the manual. 32 M o d i f i e d T e l e b i n o c u l a r Technique Format and A d m i n i s t r a t i o n The continued search f o r an e f f i c i e n t v i s i o n s c r e e n i n g technique, s u i t a b l e for school use, l e d to development in the l a t e 1970's of the M o d i f i e d T e l e b i n o c u l a r Technique (MTT) by Dr.Howard Walton, of the Southern C a l i f o r n i a School of Optometry. The MTT employs the standard Keystone t e l e b i n o c u l a r and twelve of the comprehensive b a t t e r y t e s t p l a t e s . Test s l i d e s f o r near poin t a c u i t y have been e l i m i n a t e d . A new c a r d was designed to screen myopia, amblyopia, and astigmatism. Hyperopia i s checked using the standard d i s t a n c e a c u i t y cards and a +2.00 l e n s . A l l v i s u a l problems screened by the M o d i f i e d C l i n i c a l Technique (MCT) are d e t e c t e d by the MTT: myopia, hyperopia, astigmatism, f u s i o n , suppression, anisometropia, amblyopia, muscle imbalances, and c o l o u r p e r c e p t i o n . S t e r e o p s i s i s a l s o checked by the MTT. School nurse and/or teacher o b s e r v a t i o n s p l u s eye pathology are not i n c l u d e d i n the procedure. Test I n t e r p r e t a t i o n L i k e the KTT, the MTT was not designed to y i e l d d i a g n o s i s , but an i n d i c a t i o n of whether or not a student 33 should be r e f e r r e d f o r p r o f e s s i o n a l e v a l u a t i o n . In a d d i t i o n to r e f e r r a l c r i t e r i a being i n c l u d e d i n the t e s t d i r e c t i o n s , the record form l i s t s and c a t e g o r i z e s examinee responses as being w i t h i n the expected range, the b o r d e r l i n e area, or as unsat i s f a c t o r y . Advantages Advantages of the KTT are a p p l i c a b l e to the MTT. A primary advantage i s that the technique can be a d m i n i s t e r e d by school personnel, p s y c h o l o g i s t s , and other n o n - v i s i o n s p e c i a l i s t s . T herefore the MTT overcomes the major l i m i t a t i o n of the MCT. L i m i t a t i o n s To date, r e s u l t s from only one study employing the MTT have been r e p o r t e d . In a 1976 study, Walton and h i s a s s o c i a t e s a d m i n i s t e r e d the MTT and the MCT to 102 elementary students i n Los Angeles. Based on the obtained 89.2% r e f e r r a l agreement between the two procedures, i t was concluded that the MTT and MCT are comparable. More res e a r c h i s needed before a c o n c l u s i v e d e c i s i o n can be reached on the merits of the MTT. 34 CHAPTER III - METHOD A quasi-experimental study was conducted to i n v e s t i g a t e the r e f e r r a l e f f i c a c y of the S n e l l e n , Keystone T e l e b i n o c u l a r Technique (KTT), and M o d i f i e d T e l e b i n o c u l a r Technique (MTT) a g a i n s t a standard optometric examination. S u b j e c t s Subjects were c h i l d r e n having scheduled appointments with one of f i v e o p t o m e t r i s t s p r a c t i s i n g i n Coquitlam, Surrey, and White Rock, B r i t i s h Columbia. These communities are predominantly suburban, m i d d l e - c l a s s i n c h a r a c t e r . Although the sample was not randomly s e l e c t e d , i n f o r m a l d i s c u s s i o n with s u b j e c t s and t h e i r parents i n d i c a t e d that optometric appointments were made for a v a r i e t y of reasons: parents c o n s i d e r e d a p r o f e s s i o n a l v i s u a l exam a necessary p a r t of a good h e a l t h programme, parents had concerns r e g a r d i n g t h e i r c h i l d ' s v i s i o n , or the c h i l d ' s teacher, the school nurse, or the f a m i l y doctor had recommended a p r o f e s s i o n a l e v a l u a t i o n . Thus the sample was l i k e l y r e p r e s e n t a t i v e of the r e f e r r e d p o p u l a t i o n . The s c r e e n i n g t e s t s were admi n i s t e r e d from e a r l y A p r i l u n t i l e a r l y J u l y , 1983, with students being r e g i s t e r e d in Kinder g a r t e n through f o u r t h grade. The age l i m i t s were s i x years, zero months (6-0) to nine years, eleven months (9- 35 1 1 ) . Parents/guardians of c h i l d r e n w i t h i n the age l i m i t s who had scheduled appointments with the p a r t i c i p a t i n g o p t o m e t r i s t s were informed of the study d u r i n g a r o u t i n e o f f i c e appointment reminder c a l l . Those who expressed i n t e r e s t i n the rese a r c h were given a w r i t t e n d e s c r i p t i o n of the study by o f f i c e s t a f f at the time of t h e i r c h i l d ' s appointment. Parents/guardians wishing to have t h e i r youngster p a r t i c i p a t e i n d i c a t e d t h e i r permission by completing a w r i t t e n consent form. Screening measures were administered to s i x t y - s i x s u b j e c t s . However s i x s u b j e c t s were excluded from the study one c h i l d d i d not meet l e t t e r r e c o g n i t i o n c r i t e r i a , two c h i l d r e n were younger than s i x years, two youngsters d i d not complete optometric e v a l u a t i o n s , and non-compliance during s c r e e n i n g i n v a l i d a t e d one s u b j e c t ' s responses. Thus s i x t y c h i l d r e n aged s i x years, zero months (6-0) to nine years, eleven months (9-11) p a r t i c i p a t e d i n the study. (Tables XVI and XVII i n Appendix E show s u b j e c t s c l a s s i f i e d by c h r o n o l o g i c a l age and sex r e s p e c t i v e l y . ) 36 Measures A b r i e f d e s c r i p t i o n of the content of each of the three s c r e e n i n g measures and the l e t t e r i d e n t i f i c a t i o n t e s t i s presented along with c r i t e r i a f o r s c o r i n g and i n t e r p r e t a t i o n . L e t t e r I d e n t i f i c a t i o n P r i o r to a d m i n i s t r a t i o n of the KTT and MTT each s u b j e c t was asked to i d e n t i f y upper case l e t t e r s p r i n t e d i n d i v i d u a l l y on 7.5 X 12.5 cm ( 3 X 5 inch) blank white c a r d s . The same random order of l e t t e r s was presented to each s u b j e c t . A l e t t e r was c o n s i d e r e d known i f the s u b j e c t c o r r e c t l y gave the name or sound of the l e t t e r . S e l f - c o r r e c t i o n s were counted as known. The purpose of t h i s task was to h e l p determine whether e r r o r s made on the MTT f a r and near p o i n t a c u i t y s u b t e s t s , the MTT astigmatism s u b t e s t , and on the S n e l l e n were due to v i s i o n d i f f i c u l t i e s or l i m i t e d l e t t e r i d e n t i f i c a t i o n s k i l l s . S n e l l e n The S n e l l e n c h a r t c o n s i s t s of rows of l e t t e r s , of d e c r e a s i n g s i z e presented at a d i s t a n c e of twenty f e e t ( s i x metres). School s c r e e n i n g programmes conducted by p u b l i c h e a l t h s t a f f employ e i t h e r a w a l l c h a r t or a c h a r t stand. 37 In the present study the o p t o m e t r i s t s presented the S n e l l e n by means of a p r o j e c t e d technique, which giv e s the e f f e c t i v e d i s t a n c e of twenty f e e t ( s i x metres). Each eye i s t e s t e d s e p a r a t e l y while the other i s occluded. T h i s t e s t p r i m a r i l y measures f a r p o i n t a c u i t y and myopia, although severe hyperopia and astigmatism may be d e t e c t e d . The passing c r i t e r i o n ( u s u a l l y 20/30 or 20/40) i s at the examiner's d i s c r e t i o n . In t h i s study a set p a s s i n g c r i t e r i o n of 20/40 was employed. Keystone T e l e b i n o c u l a r and M o d i f i e d T e l e b i n o c u l a r The Keystone T e l e b i n o c u l a r Technique .(KTT) and the M o d i f i e d T e l e b i n o c u l a r Technique (MTT) are b i n o c u l a r , s t e r e o s c o p i c s c r e e n i n g instruments which measure the f o l l o w i n g v i s u a l s k i l l s at f a r and near p o i n t s : monocular and b i n o c u l a r a c u i t y , muscle imbalance, f u s i o n , and amblyopia. S t e r e o p s i s and c o l o u r p e r c e p t i o n are a l s o t e s t e d at f a r p o i n t . In a d d i t i o n , the MTT screens f o r hyperopia, astigmatism, and anisometropia. A s t a n d a r d i z e d sequence of cards i s employed. The r e c o r d i n g forms i n d i c a t e whether an examinee's v i s u a l s k i l l s are s a t i s f a c t o r y , should be r e - screened, or e v a l u a t e d by a p r o f e s s i o n a l . 38 Standard Optometric Exam Among the o p t o m e t r i s t s p a r t i c i p a t i n g i n the study a consensus was obtained regarding the v i s u a l s k i l l s assessed in a standard optometric examination. These i n c l u d e t e s t s of o b j e c t i v e r e f r a c t i o n ( r e t i n o s c o p y ) , s u b j e c t i v e r e f r a c t i o n (myopia, hyperopia, astigmatism), t r o p i a s , p h o r i a s and f u s i o n at near and f a r p o i n t s , vergences and v e r s i o n s at f a r and near p o i n t s , amplitude of accommodation, s t e r e o a c u i t y , c o l o u r v i s i o n , and i n t e r n a l and e x t e r n a l o c u l a r h e a l t h . Table II shows the v i s i o n s u b t e s t s i n c l u d e d i n each s c r e e n i n g measure and a standard optometric e v a l u a t i o n . (Copies of the summary data sheet and t e s t r e c o r d forms are i n c l u d e d i n Appendix D). Assumpt ions The f o l l o w i n g assumptions were made in the study: 1. Since the study was i n v e s t i g a t i n g the e f f i c a c y of the three s c r e e n i n g measures a g a i n s t a standard optometric exam, i t was assumed a s e l f - s e l e c t e d sample would be adequate. 39 Table II V i s u a l S k i l l s Tested by Three Screening Measures and a Standard Optometric Exam VISION TEST Standard S n e l l e n KTT MTT Optometric Exam VISUAL SKILL suppression o b j e c t i v e r e f r a c t i o n ( r e t i n o s c o p y ) s u b j e c t i v e r e f r a c t i o n myopia hyperopia astigmatism f u s i o n ( f a r & near) p h o r i a s ( f a r & near) t r o p i a s ( f a r & near) vergences & v e r s i o n s amplitude of accommodat ion s t e r e o p s i s (lack of) c o l o u r v i s i o n e x t e r n a l & i n t e r n a l o c c u l a r h e a l t h ( t i s s u e exam) X X * X * X X X X X X X X X X X X X X X X X X X X X X X X X X case h i s t o r y X * severe only 2 . Subject f a t i g u e i s o f t e n a f a c t o r when t e s t i n g young c h i l d r e n . I t was assumed that the f a t i g u e d i s p l a y e d by some c h i l d r e n was not s u f f i c i e n t to d i s t o r t t e s t r e s u l t s . 3. I t was assumed that i n t e r - o p t o m e t r i s t d i f f e r e n c e s i n t e s t i n g techniques and e v a l u a t i o n were r e p r e s e n t a t i v e of those d i f f e r e n c e s found among a l l o p t o m e t r i s t s and were randomized throughout the sample. 4. Since no measure of i n t e r - o p t o m e t r i s t r e l i a b i l i t y c o u l d be obtained i t was assumed that as a l l the p a r t i c i p a t i n g o p t o m e t r i s t s had t r a i n e d at the same school of optometry, a l l are c u r r e n t l y l i c e n s e d by the B r i t i s h Columbia Optometric A s s o c i a t i o n , and a l l f o l l o w c o n v e n t i o n a l optometric procedures the optometric f i n d i n g s would be s i m i l a r . 5. An a r b i t r a r y d e c i s i o n was made to e l i m i n a t e s u b j e c t s who made more than two e r r o r s on the L e t t e r I d e n t i f i c a t i o n t e s t . I t was assumed that t h i s e r r o r c r i t e r i o n would ensure r e l i a b l e r e s u l t s on the S n e l l e n and on the MTT su b t e s t s f o r a c u i t y and astigmatism while a l l o w i n g f o r i n i t i a l t e s t a n x i e t y ; L e t t e r I d e n t i f i c a t i o n was the f i r s t t e s t 41 admini s t e r e d . 6 . Although d i s c r e t e r e f e r r a l c a t e g o r i e s are given f o r the KTT and MTT, the v i s u a l s k i l l s assessed are assumed to e x i s t along a performance cont inuum. Procedures Test A d m i n i s t r a t i o n Each s u b j e c t , i d e n t i f i e d by number, was administered a l l s c reening measures and a l e t t e r i d e n t i f i c a t i o n t e s t i n a d d i t i o n to a standard optometric examination. Subjects wearing g l a s s s e s were screened without t h e i r g l a s s e s . S e v e r a l t e s t items are common to the Keystone T e l e b i n o c u l a r Technique (KTT) and the M o d i f i e d T e l e b i n o c u l a r Technique (MTT). These items were admi n i s t e r e d only once. Odd numbered s u b j e c t s were admi n i s t e r e d the complete KTT fol l o w e d by the remaining items from the MTT. Even numbered s u b j e c t s were given a l l items from the MTT followed by the remaining items from the KTT. Table III summarizes the order of t e s t a d m i n i s t r a t i o n . 42 Table III A d m i n i s t r a t i o n Order of V i s u a l T e s t s Odd Numbered Subjects 1. Standard Optometric Exam & S n e l l e n 2. L e t t e r I d e n t i f i c a t i o n 3. KTT subt e s t s (1-14 i n c l u s i v e ) 4. MTT subt e s t s (4W,4 1/2,5,6,12) 5. R e t e s t i n g of KTT subtests scored as r e t e s t 6. R e t e s t i n g of MTT subtests scored as r e t e s t Even Numbered Subjects 1. Standard Optometric Exam & S n e l l e n 2. L e t t e r I d e n t i f i c a t i o n 3. MTT subt e s t s (1-12 i n c l u s i v e ) 4. KTT subtests (4 1/2,5,6,12,13,14) 5. R e t e s t i n g of MTT subt e s t s scored as r e t e s t 6. R e t e s t i n g of KTT subtests scored as r e t e s t Note. See samples of p r o t o c o l s i n Appendix D f o r KTT and MTT subtest headings. 43 The l e t t e r i d e n t i f i c a t i o n t e s t , the KTT, and the MTT were admi n i s t e r e d by the r e s e a r c h e r . The S n e l l e n was adm i n i s t e r e d by the o p t o m e t r i s t s as part of the standard optometric exam. F i f t y - s i x s u b j e c t s were seen by the op t o m e t r i s t and then administered the scre e n i n g measures. Four s u b j e c t s underwent v i s i o n s c r e e n i n g p r i o r to c l i n i c a l examination. Whether a subject was screened before or a f t e r optometric e v a l u a t i o n depended upon which best f a c i l i t a t e d optometric bookings. Performance on the KTT and the MTT was not compared to r e s u l t s from the S n e l l e n or the optometric exam u n t i l a f t e r a subject had completed a l l t e s t i n g . Recording Data Consistency i n r e c o r d i n g s u b j e c t s ' performance was f a c i l i t a t e d by use of standard r e c o r d i n g forms which accompany the KTT and MTT. Data sheets were used f o r r e c o r d i n g l e t t e r i d e n t i f i c a t i o n responses and o v e r a l l performance on each sc r e e n i n g measure and the standard optometric exam. (See Appendix D f o r c o p i e s of a l l r e c o r d i n g forms.) 44 Inc o n s i s t e n c y in r e c o r d i n g and i n t e r p r e t i n g s u b j e c t s ' responses on l e t t e r i d e n t i f i c a t i o n , the KTT, and the MTT was reduced by these measures being a d m i n i s t e r e d by one examiner. Optometric Exam The v a l i d i t y of the three s c r e e n i n g measures i n v e s t i g a t e d was i n c r e a s e d by i n c l u d i n g p a t i e n t s from f i v e o p t o m e t r i s t s . The b e n e f i t s gained were c o n s i d e r e d to out weigh l i m i t a t i o n s due to i n t e r - o p t o m e t r i s t d i f f e r e n c e s . Such d i f f e r e n c e s c o u l d have stemmed from v a r i a t i o n i n a d m i n i s t r a t i o n techniques or e v a l u a t i o n c r i t e r i a employed du r i n g the standard optometric exam. D i f f e r e n c e s i n technique may a l s o have occurred d u r i n g S n e l l e n a d m i n i s t r a t i o n . For t h i s study the same S n e l l e n p a s s i n g c r i t e r i o n (20/40) was used by a l l o p t o m e t r i s t s . R e l i a b i l i t y of i n t e r - o p t o m e t r i s t f i n d i n g s would have r e q u i r e d s u b j e c t s to be seen by more than one opt o m e t r i s t which was not f e a s i b l e given time and economic r e s t r a i n t s . Other T e s t i n g F a c t o r s Other f a c t o r s which may have biased s c r e e n i n g r e s u l t s were parent o b s e r v a t i o n and sub j e c t f a t i g u e . Although the w r i t t e n d e s c r i p t i o n of the study suggested s u b j e c t s be 45 screened alone, in nine cases e i t h e r the c h i l d or parent requested the parent be p r e s e n t . As in any t e s t i n g s i t u a t i o n with young c h i l d r e n f a t i g u e was e x h i b i t e d by some youngsters, but a b r i e f pause to d i s c u s s school or t h e i r o u t s i d e i n t e r e s t s was s u f f i c i e n t to r e s t o r e i n t e r e s t i n the scre e n i n g t a s k s . Therefore the s u b j e c t i v e judgement was made that f a t i g u e d i d not b i a s t e s t r e s u l t s . Scoring and I n t e r p r e t a t i o n L e t t e r I d e n t i f i c a t i o n . A 92% (24/26) i d e n t i f i c a t i o n c r i t e r i o n was co n s i d e r e d necessary f o r r e l i a b l e performance to be obtained on the MTT and S n e l l e n . Subjects not meeting t h i s c r i t e r i a were not i n c l u d e d i n the study. S n e l l e n . A pass i n g c r i t e r i o n of 20/40, fo r each eye, was employed f o r e v a l u a t i n g S n e l l e n performance. T h i s c r i t e r i o n was recommended by the p a r t i c i p a t i n g o p t o m e t r i s t s . 46 Keystone and M o d i f i e d T e l e b i n o c u l a r Techniques. In order to examine the e f f i c a c y of the KTT and the MTT the e s t a b l i s h e d s c o r i n g procedures and performance c r i t e r i a , as i n d i c a t e d on the t e s t r e c o r d forms and in the t e s t d i r e c t i o n s , were foll o w e d . U n s a t i s f a c t o r y performance on a subtest was i n t e r p r e t e d as suggesting the need f o r p r o f e s s i o n a l e v a l u a t i o n , rather than as being d i a g n o s t i c of a d e f i c i t i n the v i s u a l s k i l l covered. Use of commercially a v a i l a b l e record forms f o r the KTT and MTT ensured that r e c o r d i n g of s u b j e c t s ' responses was c o n s i s t e n t and o b j e c t i v e . Responses f a l l i n g i n the Expected Response range or i n the Retest ( B o r d e r l i n e ) category were c l a s s i f i e d as passes (no r e f e r r a l i n d i c a t e d ) . Responses in the U n s a t i s f a c t o r y range were c l a s s i f i e d as a r e f e r r a l f o r subt e s t s measuring simultaneous v i s i o n ( t e s t 1 - KTT & MTT), v e r t i c a l posture ( t e s t 2 - KTT & MTT), f a r point a c u i t y ( t e s t s 4 1/2, 5, & 6 - KTT; t e s t 4W - MTT), and near poin t a c u i t y ( t e s t 12 - MTT). U n s a t i s f a c t o r y performance on c o l o u r v i s i o n ( t e s t s 8 & 9 - KTT & MTT) was noted, but was not s u f f i c i e n t by i t s e l f to c o n s t i t u t e a r e f e r r a l . Age was c o n s i d e r e d i n i n t e r p r e t i n g , performance on l a t e r a l posture ( t e s t s 3 & 10 KTT & MTT), f u s i o n ( t e s t s 4 & 11 - KTT & MTT), s t e r e o p s i s ( t e s t 7 - KTT & MTT), and near p o i n t a c u i t y ( t e s t s 12, 13, & 14 - KTT). The i n t e r p r e t a t i o n suggestions given in the t e s t d i r e c t i o n s f o r these su b t e s t s were followed when e v a l u a t i n g 47 responses for six and seven year olds. Standard Optometric Exam. Performance of subjects on the standard optometric exam was evaluated by the optometrists' professional judgement. Those children who were judged to require corrective lenses (glasses), contact lenses, therapy, or continued observation were c l a s s i f i e d as needing professional care (positive r e f e r r a l ) . Referral Categories Based on a comparison of screening and optometric findings, subjects were categorized on each screening measure as a(n): positive r e f e r r a l - r e f e r r a l indicated by both screening measure and optometric exam negative r e f e r r a l - r e f e r r a l not indicated by screening measure nor by optmetric exam 48 o v e r r e f e r r a l ( f a l s e p o s i t i v e ) - r e f e r r e d by screening measure, but not r e q u i r i n g p r o f e s s i o n a l c a r e u n d e r r e f e r r a l ( f a l s e negative) - r e f e r r a l not i n d i c a t e d by s c r e e n i n g measure, but r e q u i r i n g p r o f e s s i o n a l care Table IV summarizes r e f e r r a l c a t e g o r i e s . Table IV Types of R e f e r r a l s SCREENING TEST r e f e r r a l i n d i c a t e d no r e f e r r a l i n d i c a t e d OPTOMETRIC EXAM p r o f e s s i o n a l care r e q u i r e d p o s i t i v e r e f e r r a l u n d e r r e f e r r a l ( f a l s e negative) p r o f e s s i o n a l care not requi red o v e r r e f e r r a l negative r e f e r r a l ( f a l s e p o s i t i v e ) 49 S c o r i n g R e l i a b i l i t y As a check on the accuracy of the r e s e a r c h e r ' s s c o r i n g and i n t e r p r e t i n g of the KTT and the MTT 30 p r o t o c o l s from each measure were re - e v a l u a t e d by an independent s c o r e r . Optometrist Howard Walton, of the Southern C a l i f o r n i a C o l l e g e of Optometry, developer of the M o d i f i e d T e l e b i n o c u l a r Technique, d i d the independent s c o r i n g . The 60 p r o t o c o l s scored by Dr. Walton i n c l u d e d a l l those in which there might be c o n t r o v e r s y over whether or not the c h i l d should be r e f e r r e d for p r o f e s s i o n a l e v a l u a t i o n (26 each of KTT and MTT), p l u s others selected, at random (4 each of KTT and MTT). Agreement between the researcher and the independent sc o r e r with respect to the r e f e r r a l s t a t u s of s u b j e c t s i s shown in Table V. Consensus on r e f e r r a l was present f o r 29 MTT p r o t o c o l s . D i f f e r e n t i n t e r p r e t a t i o n s of the i n c o n s i s t e n t responses given on the hyperopia subtest r e s u l t e d i n c o n f l i c t i n g r e f e r r a l s being made for one s u b j e c t . Phi c o e f f i c i e n t ( G u i l f o r d , 1965) and chi-square analyses comparing s c o r i n g agreement on the MTT found s i g n i f i c a n t agreement between the researcher and the independent scorer regarding r e f e r r a l s t a t u s , 0=.93, X 2 0 ) = 2 6 . 1 7 , p <.001. R e f e r r a l agreement e x i s t e d f o r 26 KTT p r o t o c o l s . Disagreement on the remaining four p r o t o c o l s stemmed from d i f f e r e n t i n t e r p r e t a t i o n s of performance on the muscle balance, s t e r e o p s i s , and near p o i n t a c u i t y s u b t e s t s 50 where age may i n f l u e n c e responses. On these s u b t e s t s the e r r o r s made by young c h i l d r e n may r e f l e c t v i s u a l immaturity r a t h e r than a v i s u a l anomaly. The KTT manual i s not s p e c i f i c in whether the e r r o r responses of young c h i l d r e n should be i n t e r p r e t e d as passes or r e f e r r a l s . S t a t i s t i c a l a nalyses y i e l d e d lower, but s t i l l s i g n i f i c a n t s c o r i n g agreement f o r the KTT, 0=.75, X 2(1)=16.83, p_ <.001. These r e s u l t s i n d i c a t e d that the r e s e a r c h e r ' s s c o r i n g and i n t e r p r e t i n g of the KTT and the MTT were s u f f i c i e n t l y a c c urate to y i e l d r e l i a b l e s c r e e n i n g data. Table V Agreement of R e f e r r a l Status on KTT and MTT p r o t o c o l s by the researcher and the independent s c o r e r Agreed no. C T%) P i sagreed no. (%) Keystone T e l e b i n o c u l a r 26 (87) 4 (13) M o d i f i e d T e l e b i n o c u l a r 29 (97) (3) Note. S c o r i n g on 30 p r o t o c o l s of each measure was compared. 51 .Data A n a l y s i s The i n t e n t of the study was to compare the frequency of r e f e r r a l c a t e g o r i e s f o r each s c r e e n i n g measure ag a i n s t r e f e r r a l s from a standard optometric exam. R e s u l t s were sub j e c t e d to ch i - s q u a r e and phi c o e f f i c i e n t a n a l y s e s . Delimi t a t ions The d e l i m i t a t i o n s of the study concerned the sample. C h i l d r e n aged 6-0 to 9-11 were s e l e c t e d for the study. There were few c h i l d r e n i n each age category (see Table XVII, Appendix E ) . Subjects were only those c h i l d r e n who had scheduled . appointments with the p a r t i c i p a t i n g o p t o m e t r i s t s and whose parents consented to t h e i r p a r t i c i p a t i n g i n the study. 52 CHAPTER IV - RESULTS Data, obtained from a sample of 60 primary students, on the r e f e r r a l e f f i c a c y of the MTT, the KTT, and the S n e l l e n are presented. Each s c r e e n i n g measure i s compared to the standard optometric exam f o r v i s u a l s k i l l s t e s t e d and e f f i c a c y of r e f e r r a l s . The s i g n i f i c a n c e of the d i f f e r e n t r e f e r r a l r a t e s among the three s c r e e n i n g measures i s d i s c u s s e d . V i s u a l S k i l l s Tested Chi-square analyses were performed to determine whether the v i s u a l s k i l l s measured by each s c r e e n i n g measure and the standard optometric exam were independent or r e l a t e d . F o l l o w i n g the recommendation of Hopkins and G l a s s (1978) the Yates c o r r e c t i o n f o r c o n t i n u i t y was not a p p l i e d . Phi c o e f f i c i e n t s were computed to measure the s t r e n g t h of the r e l a t i o n s h i p between each sc r e e n i n g measure and the standard optometric exam. These r e s u l t s are shown in Table VI. Standard scores (Hopkins & G l a s s , 1978) were computed from the phi c o e f f i c i e n t s to determine whether the s c r e e n i n g measures d i f f e r e d s i g n i f i c a n t l y i n t h e i r agreement with the standard optometric exam. These r e s u l t s are presented i n Table V I I . The s i g n i f i c a n t r e s u l t s obtained from the chi-square 53 analyses (Table VI) i n d i c a t e that each of the screening measures t e s t e d v i s u a l s k i l l s covered by the optometric exam. The d i f f e r e n c e s between the phi c o e f f i c i e n t s , as shown by the 1 scores in Table V I I , are not s i g n i f i c a n t . These r e s u l t s i n d i c a t e that each of the three measures s t u d i e d does t e s t e s s e n t i a l v i s u a l s k i l l s , but they do not show the e f f i c a c y of the measures. Table VI Comparison 1 and Strength of Agreement 2 of the V i s u a l S k i l l s t e s t e d by Three Screening Measures and a Standard Optometric Exam X 2 MTT and Standard Optometric Exam 17.94* . 55 KTT and Standard Optometric Exam 6.70* .33 S n e l l e n and Standard Optometric Exam 7.98* .36 1Chi-square a n a l y s i s 2 P h i c o e f f i c i e n t a n a l y s i s * 2 < . 0 1 54 Table VII Standard Score Comparisons of the Strength of Agreememt {$) between Three Screening Measures and a Standard Optometric Exam (SOE) Z MTT and SOE vs KTT and SOE 1.47, ns MTT and SOE vs S n e l l e n and SOE 1.29, ns KTT and SOE vs S n e l l e n and SOE .181, ns p>.05 R e f e r r a l E f f i c a c y Answers were sought to the f o l l o w i n g q u e s t i o n s f o r the sample of 60 primary aged optometric p a t i e n t s . Question 1 - Does the MTT have a g r e a t e r e f f i c a c y (fewer under- or o v e r r e f e r r a l s ) than the KTT when the standard optometric examination i s used as the c r i t e r i o n f o r r e f e r r a l ? 55 Question 2 - Does the MTT have a grea t e r e f f i c a c y (fewer under- or over r e f e r r a l s ) than the S n e l l e n when the standard optometric examination i s used as the c r i t e r i o n f o r r e f e r r a l ? Question 3 - Does the KTT have a grea t e r e f f i c a c y (fewer under- or o v e r r e f e r r a l s ) than the S n e l l e n when the standard optometric examination i s used as the c r i t e r i o n f o r r e f e r r a l ? F i n d i n g s R e f e r r a l e f f i c a c y was determined by comparison of the number of r e f e r r a l s , in each category, made by each scr e e n i n g measure a g a i n s t f i n d i n g s from the standard optometric exam. Table VIII presents the r e f e r r a l r a t e s of the three screening measures, while Table IX summarizes the number and percentage of c o r r e c t and i n c o r r e c t r e f e r r a l s f o r each measure. The MTT made the most c o r r e c t r e f e r r a l s (77%), with fewer than a qu a r t e r of the s u b j e c t s being 56 i n c o r r e c t l y r e f e r r e d . Most of the e r r o r s (10/14) made by the MTT were o v e r r e f e r r a l s . In comparison, the KTT and the S n e l l e n both erroneously r e f e r r e d almost one t h i r d of the sample. The KTT made 18 o v e r r e f e r r a l s and 11 u n d e r r e f e r r a l s . The S n e l l e n ' s e r r o r r a t e was composed predominately of u n d e r r e f e r r a l s . I t d i d not r e f e r 30% (18/60) of the s u b j e c t s who r e q u i r e d p r o f e s s i o n a l care. These r e f e r r a l r a t e s p e r t a i n to the e f f i c a c y of the three s c r e e n i n g measures s t u d i e d . They should not be i n t e r p r e t e d as r e p r e s e n t i n g the p r o p o r t i o n of B.C. primary c h i l d r e n w i t h i n each r e f e r r a l category. The c hi-square analyses computed to determine whether the obtained r e f e r r a l r a t e s were s i g n i f i c a n t l y d i f f e r e n t are shown i n Table X. These f i n d i n g s are d i s c u s s e d below in r e l a t i o n to the research q u e s t i o n s posed. 57 Table VIII Number and Percentage 1 of S i x t y Subjects i n Each R e f e r r a l Category, per Screening Measure as Compared to a Standard Optometric Exam REFERRAL CATEGORIES C o r r e c t l y R e f e r r e d I n c o r r e c t l y R e f e r r e d p o s i t i v e negative over under r e f e r r a l s r e f e r r a l s r e f e r r a l s r e f e r r a l s no.(%) no.(%) SCREENING MEASURE MTT KTT S n e l l e n 21 (35) 14 (23) 7 (12) 25 (42) 27 (45) 34 (57) no.(%) 10 (17) 8 (13) 1 (2) no.(%) 4 (7) 11 (18) 18 ' (-30) 1 Percentage values have been rounded. 58 Table IX Summary of C o r r e c t and I n c o r r e c t R e f e r r a l s 1 f o r Each Screening Measure as Compared to a Standard Optometric Exam REFERRALS C o r r e c t R e f e r r a l s 2 I n c o r r e c t R e f e r r a l s 3 no. (%)" no. T i l SCREENING MEASURE MTT 46 (77) 1 4 (23) KTT 41 (68) 1 9 (32) S n e l l e n 41 (68) 1 9 (32) ^=60 for each scr e e n i n g measure 2 C o r r e c t R e f e r r a l s - p o s i t i v e p l u s negative r e f e r r a l s 3 I n c o r r e c t R e f e r r a l s - o v e r r e f e r r a l s p l u s u n d e r r e f e r r a l s "Percentage values have been rounded. Table X Chi-square Comparisons of the Number of R e f e r r a l s per Category between Screening Measures REFERRAL CATEGORIES p o s i t i v e negative over under r e f e r r a l s r e f e r r a l s r e f e r r a l s r e f e r r a l s SCREENING MEASURE MTT vs KTT 1.4000 .0769 .2223 3.2667 MTT vs S n e l l e n 7.0000** 1.3729 7.3636** 8.9091** KTT vs S n e l l e n 2.3334 .8033 5.4445* 1.6896 *2<-05 **P<.01 59 Question 1 Chi-square a n a l y s i s i n d i c a t e d there was no s i g n i f i c a n t d i f f e r e n c e between the MTT and the KTT f o r e i t h e r o v e r r e f e r r a l s or u n d e r r e f e r r a l s . Question 2 A s i g n i f i c a n t d i f f e r e n c e was found between the MTT and the S n e l l e n with respect to o v e r r e f e r r a l s , X 2 ( 1 ) = 7 . 3636, p_ <.01. The fewer o v e r r e f e r r a l s made by the S n e l l e n i n d i c a t e • i t was the more accurate t e s t f o r t h i s r e f e r r a l category. The d i f f e r e n c e between the MTT and the S n e l l e n f o r under r e f e r r a l s was a l s o s i g n i f i c a n t , X2 { 1 ) =8. 909 1 , p_ <.01. The MTT made fewer u n d e r r e f e r r a l s and t h e r e f o r e had grea t e r e f f i c a c y than the S n e l l e n f o r t h i s r e f e r r a l c a t e g o r y . Question 3 Chi-square a n a l y s i s was s i g n i f i c a n t f o r the d i f f e r e n c e between the KTT and the S n e l l e n f o r o v e r r e f e r r a l s , X 2 ( 1 ) = 5.4445, p <.05. The S n e l l e n , with i t s fewer o v e r r e f e r r a l s , had greater e f f i c a c y than the KTT f o r the sample s t u d i e d . No s i g n i f i c a n t d i f f e r e n c e was found between the KTT and the S n e l l e n with respect to u n d e r r e f e r r a l s . 60 Comparisons f o r P o s i t i v e and Negative R e f e r r a l s Comparisons between a l l scr e e n i n g measures with respect to i d e n t i f y i n g negative r e f e r r a l s ( s u b j e c t s not r e q u i r i n g p r o f e s s i o n a l care) were non s i g n i f i c a n t . For p o s i t i v e r e f e r r a l s ( s u b j e c t s i d e n t i f i e d as r e q u i r i n g p r o f e s s i o n a l care) the comparison between the MTT and the S n e l l e n was s i g n i f i c a n t , X 2(1)=7.000, g<.01. The g r e a t e r number of p o s i t i v e r e f e r r a l s i d e n t i f i e d by the MTT i n d i c a t e s i t had grea t e r e f f i c a c y than the S n e l l e n f o r t h i s r e f e r r a l c ategory. D i s c u s s i o n The study was concerned with the e f f i c a c y of three v i s i o n s c r e e n i n g measures rather than e s t a b l i s h i n g r e f e r r a l r a t e s f o r v i s u a l anomalies among primary students. T h e r e f o r e the f i n d i n g s of the study should not be i n t e r p r e t e d as r e f e r r a l r a t e s f o r the general p o p u l a t i o n of B r i t i s h Columbia primary students. What the data do i n d i c a t e i s how the S n e l l e n , the Keystone T e l e b i n o c u l a r (KTT), and the M o d i f i e d T e l e b i n o c u l a r Technique (MTT) compare with each other and to the standard optometric exam with r e s p e c t to the frequency of p o s i t i v e r e f e r r a l s , n egative r e f e r r a l s , o v e r r e f e r r a l s , and u n d e r r e f e r r a l s . The number of o v e r r e f e r r a l s and u n d e r r e f e r r a l s are of the most concern i n any v i s i o n s c r e e n i n g programme. 61 O v e r r e f e r r a l s , which u n n e c e s s a r i l y u t i l i z e p r o f e s s i o n a l s e r v i c e s , were judged to be l e s s s e r i o u s than u n d e r r e f e r r a l s . The l a t t e r are those examinees who do r e q u i r e p r o f e s s i o n a l a t t e n t i o n , but are not i d e n t i f i e d by the v i s i o n s c r e e n i n g programme. The undetected v i s u a l d i f f i c u l t i e s of these c h i l d r e n may develop i n t o more s e r i o u s v i s u a l anomalies and/or hinder t h e i r school performance. A n a l y s i s i n d i c a t e d that the MTT and the KTT d i d not d i f f e r s i g n i f i c a n t l y i n t h e i r r e f e r r a l e f f i c a c y f o r any r e f e r r a l category (see Table X). The f a c t that a number of MTT and KTT subt e s t s u t i l i z e the same t e s t p l a t e s would p a r t l y account f o r these r e s u l t s . However, some d i f f e r e n t i a t i o n might be expected given the MTT's more s p e c i f i c r e f e r r a l c r i t e r i a , p a r t i c u l a r l y with respect to developmental f a c t o r s . Although s t a t i s t i c a l l y s i g n i f i c a n t d i f f e r e n c e s were not found f o r the sample t e s t e d , the obtained c h i - s q u a r e comparison of the number of u n d e r r e f e r r a l s made by the two measures approached s i g n i f i c a n c e at the .05 l e v e l . Therefore i t co u l d be hypothesized that a l a r g e r sample s i z e would have y i e l d e d a s i g n i f i c a n t d i f f e r e n c e f o r t h i s r e f e r r a l c a t e gory. S t a t i s t i c a l l y , the MTT had g r e a t e r e f f i c a c y than the S n e l l e n f o r p o s i t i v e r e f e r r a l s and u n d e r r e f e r r a l s . The S n e l l e n made fewer o v e r r e f e r r a l s . No s i g n i f i c a n t d i f f e r e n c e was found f o r negative r e f e r r a l s . If a choice were to be made between using the MTT or the S n e l l e n i n a school v i s i o n 62 scr e e n i n g programme the obtained data would support the MTT. Th i s c h o i c e would be l a r g e l y determined by the MTT's greater e f f i c a c y with respect to u n d e r r e f e r r a l s . The KTT and S n e l l e n d i d not d i f f e r s i g n i f i c a n t l y i n t h e i r r e f e r r a l e f f i c a c y except f o r o v e r r e f e r r a l s . The S n e l l e n made fewer o v e r r e f e r r a l s and thus had the greater e f f i c a c y . A s i m i l a r r e l a t i o n s h i p was found between the MTT and the S n e l l e n . F a c t o r s which may have i n f l u e n c e d these f i n d i n g s are the number and type of v i s u a l s k i l l s screened by a measure or the sample t e s t e d . The S n e l l e n p r i m a r i l y measures f a r p o i n t a c u i t y . An important advantage, of the KTT and MTT i s t h e i r comprehensiveness. However, because these measures screen a number of f a r and near p o i n t s k i l l s there e x i s t s a gr e a t e r p o s s i b i l i t y of r e f e r r a l e r r o r than on the S n e l l e n . That i s , the more t e s t s that are administered d u r i n g a v i s i o n s c r e e n i n g , the gr e a t e r the op p o r t u n i t y f o r e r r o r s to occur. The r e s u l t s shown in Table VIII show the e r r o r s made by the KTT and MTT tended to be o v e r r e f e r r a l s , r a t h e r than the more s e r i o u s u n d e r r e f e r r a l s made by the S n e l l e n . S e v e r a l s u b t e s t s on the KTT and MTT are i n f l u e n c e d by developmental f a c t o r s (e.g., muscle balance, s t e r e o p s i s ) again i n c r e a s i n g the p o t e n t i a l f o r e r r o r s . D i f f e r e n t r e s u l t s might have been obtained had the sample been randomly s e l e c t e d , been l a r g e r , and/or had i n c l u d e d students from a wider grade range. Although i t i s d i f f i c u l t to make d i r e c t comparisons 63 between s t u d i e s r e g a r d i n g a t e s t ' s e f f i c a c y , because of d i f f e r e n c e s i n samples, procedures, and r e f e r r a l c r i t e r i a , such comparisons can sometimes give an i n d i c a t i o n of whether a p a r t i c u l a r t e s t tends to c o n s i s t e n t l y o v e r r e f e r or u n d e r r e f e r . With t h i s i n mind, the present r e s u l t s are compared to e a r l i e r s t u d i e s i n v o l v i n g the S n e l l e n , the KTT, and the MTT. S n e l l e n In the present study the S n e l l e n had an u n d e r r e f e r r a l r a t e of 30% (see Table V I I I ) which i s c o n s i s t e n t with the 25% r a t e r e p o r t e d by Spache (1965) for the 1949 S t . L o u i s study. E i s n e r and Oglesby (1971) re p o r t e d S n e l l e n u n d e r r e f e r r a l s that ranged from 16.4% to 51.3%. The 2% (see Table V I I I ) o v e r r e f e r r a l r a t e obtained i n the present study i s s i g n i f i c a n t l y lower than the 32.7% to 35.4% r e p o r t e d by E i s n e r and Oglesby (1971). T h i s i s probably due to the s i z e and nature of the sample t e s t e d i n t h i s study. Had a l a r g e number of c h i l d r e n , randomly s e l e c t e d from the general primary student p o p u l a t i o n , been t e s t e d d i f f e r e n t r e s u l t s may have been obtained. 64 Keystone T e l e b i n o c u l a r Technique Table XI compares the percentages of d i f f e r e n t r e f e r r a l s obtained f o r the KTT i n the present study to those found i n the 1956 t e s t i n g of the Orinda study (Blum et a l . , 1959). In the present study r e f e r r a l s were higher i n a l l c a t e g o r i e s , except negative r e f e r r a l s . D i f f e r e n c e s in the sample may have i n f l u e n c e d the f i n d i n g s of the two s t u d i e s . The Orinda sample was randomly s e l e c t e d from a l a r g e school p o p u l a t i o n , while the present sample was drawn from f i v e optometric p r a c t i c e s . Table XI Comparison of KTT R e f e r r a l Rates for Primary Students in the Present Study and i n the 1956 t e s t i n g of the Orinda Study REFERRAL CATEGORIES pos i t i ve r e f e r r a l s negative over r e f e r r a l s r e f e r r a l s under r e f e r r a l s Orinda Study,1956 1 9% 76% 6% 9% Present Study 23% 45% 1 3% 1 8% Summarized from Blum et a l (1959) 65 M o d i f i e d T e l e b i n o c u l a r Technique In a 1976 study Walton compared the MTT to the MCT and obtained a r e f e r r a l agreement of 89.2%. The present study found t h a t , of the three s c r e e n i n g measures t e s t e d , the MTT had the h i g h e s t percentage (77%) of c o r r e c t r e f e r r a l s (see Table IX). These r e s u l t s suggest the MTT would be a u s e f u l v i s i o n s c r e e n i n g measure that c o u l d be given by n o n - v i s i o n s p e c i a l i s t s , p a r t i c u l a r l y where p r o f e s s i o n a l v i s i o n s e r v i c e s are l i m i t e d . 66 CHAPTER V - SUMMARY AND RECOMMENDATIONS Although the a c t u a l i n c i d e n c e of c h i l d r e n r e q u i r i n g p r o f e s s i o n a l v i s i o n care does not yet seem to have been e s t a b l i s h e d , the r e p o r t e d r a t e s i n d i c a t e that a v a r i e t y of v i s u a l anomalies occur i n s u f f i c i e n t numbers among c h i l d r e n to warrant recommendation of a comprehensive v i s i o n s c reening programme w i t h i n the school system (Coleman, 1970; Cross, 1975; Harley & Lawrence, 1977; J e r v i s , 1978; O n t a r i o M i n i s t r y of Health, 1976; Province of B r i t i s h Columbia, M i n i s t r y of Health, 1977; Rosen, 1966; and Woo & Badger, 1978). The purpose of the present study was to i n v e s t i g a t e which of three v i s i o n s c r e e n i n g measures would be the most accurate i n i d e n t i f y i n g students i n need of p r o f e s s i o n a l a t t e n t i o n and c o u l d be a d m i n i s t e r e d by n o n - v i s i o n s p e c i a l i s t s (e.g., e d u c a t i o n a l p s y c h o l o g i s t s , school nurses) in B r i t i s h Columbia s c h o o l s . A q u a s i - e x p e r i m e n t a l study was conducted to i n v e s t i g a t e the r e f e r r a l e f f i c a c y of the Keystone T e l e b i n o c u l a r Technique (KTT), the M o d i f i e d T e l e b i n o c u l a r Technique (MTT), and the S n e l l e n a g a i n s t a standard optometric exam. 67 Screening Measures No screening measure, r e g a r d l e s s of i t s comprehensiveness, i s e q u i v a l e n t to, or r e p l a c e s , a c l i n i c a l examination. Screening r e s u l t s do not equal d i a g n o s i s . T h i s l i m i t a t i o n must be c o n s i d e r e d when e v a l u a t i n g e i t h e r an i n d i v i d u a l ' s screening performance or a measure's o v e r a l l ef f i c a c y . S n e l l e n The S n e l l e n c o n s i s t s of rows of l e t t e r s , of d e c r e a s i n g s i z e , presented on e i t h e r a w a l l c h a r t or a l i g h t stand at a d i s t a n c e of twenty feet ( s i x metres). Both eyes remain open du r i n g t e s t i n g . Each eye i s t e s t e d s e p a r a t e l y while the other i s occluded. The s t a n d a r d i z e d a d m i n i s t r a t i o n procedure of the N a t i o n a l S o c i e t y for the Prevention of B l i n d n e s s (Harley & Lawrence, 1977) recommends both eyes f i r s t be t e s t e d together. However, the l i t e r a t u r e surveyed d i d not i n d i c a t e t h i s procedure to be commonly followed. The S n e l l e n p r i m a r i l y measures f a r p o i n t a c u i t y and myopia, although severe hyperopia and astigmatism may be d e t e c t e d . V i s u a l a c u i t y i s expressed as a f r a c t i o n ; the numerator r e f e r r i n g to the s u b j e c t ' s d i s t a n c e from the c h a r t , the denominator to the s m a l l e s t l e t t e r s seen. Standard v i s i o n i s r e p o r t e d as 20/20. Passing c r i t e r i o n i s u s u a l l y 20/30 or 20/40 and i s set at the examiner's d i s c r e t i o n . As the S n e l l e n can be q u i c k l y and e a s i l y administered 68 and i s inexpensive i t i s a widely used t e s t . However i t i s not without l i m i t a t i o n s . Standardized t e s t i n g c o n d i t i o n s can be e a s i l y v i o l a t e d . I n c o n s i s t e n c i e s can occur in l i g h t i n g and d i s t a n c e from the c h a r t . Students can c l o s e or squint the occluded eye. Several students may be present in the t e s t i n g room and thus have the o p p o r t u n i t y to study or memorize the c h a r t p r i o r to being t e s t e d . A s t a n d a r d i z e d a d m i n i s t r a t i o n procedure i s l a c k i n g and there i s no set r e f e r r a l c r i t e r i o n . Perhaps the g r e a t e s t l i m i t a t i o n i s the t e s t ' s r e s t r i c t e d content. For example, near p o i n t a c u i t y i s not checked unless an a l t e r n a t e form i s g i v e n . The l i t e r a t u r e d i d not report t h i s to be a common procedure in most school v i s i o n s c r e e n i n g programmes employing the S n e l l e n , yet a s i g n i f i c a n t amount of near p o i n t work i s r e q u i r e d of students. Keystone T e l e b i n o c u l a r and M o d i f i e d T e l e b i n o c u l a r The Keystone T e l e b i n o c u l a r Technique (KTT) and the M o d i f i e d T e l e b i n o c u l a r Technique (MTT) are b i n o c u l a r , s t e r e o s c o p i c screening instruments which measure the f o l l o w i n g v i s u a l s k i l l s at f a r and near p o i n t s : monocular and b i n o c u l a r a c u i t y , muscle imbalance, f u s i o n , and amblyopia. S t e r e o p s i s and c o l o u r v i s i o n are a l s o t e s t e d at f a r p o i n t . The MTT a l s o screens f o r hyperopia, astigmatism, and a n i s o m e t r o p i a . A s t a n d a r d i z e d sequence of cards i s presented f o l l o w i n g a s t a n d a r d i z e d a d m i n i s t r a t i o n procedure. The eyes are t e s t e d s e p a r a t e l y and/or together on s p e c i f i c 69 s u b t e s t s . Recording forms i n d i c a t e whether the examinee's v i s u a l s k i l l s are s a t i s f a c t o r y , should be re-screened, or eva l u a t e d by a p r o f e s s i o n a l . O v e r a l l performance on both the KTT and the MTT i s eval u a t e d i n determining whether a r e f e r r a l should be made. The subt e s t s have not been designed to y i e l d d i a g n o s t i c data, t h e r e f o r e r e s u l t s should not be compared to f i n d i n g s from c l i n i c a l t e s t s of the same name. The main advantages of the KTT and the MTT i n c l u d e s t a n d a r d i z e d procedures f o r t e s t i n g , r e c o r d i n g , and i n t e r p r e t i n g a v a r i e t y of v i s u a l s k i l l s at f a r and near p o i n t d i s t a n c e s . A l s o important i s that these measures can be administered by n o n - v i s i o n p r o f e s s i o n a l s a f t e r b r i e f t r a i n i n g . Other advantages i n c l u d e an i n t e r n a l l i g h t source which p r o v i d e s constant i l l u m i n a t i o n between a d m i n i s t r a t i o n s , a compact s i z e which makes i t p o r t a b l e , and a height adjustment mechanism. There are l i m i t a t i o n s f o r both the KTT and the MTT. The occluder between the lenses may be too wide f o r some young c h i l d r e n causing them to move t h e i r head from s i d e to si d e d i s t o r t i n g t e s t accuracy. Both measures are c o n s i d e r a b l y more expensive than the S n e l l e n . C o n t r o v e r s i a l r e f e r r a l r a t e s have been repo r t e d f o r the KTT (Harley & Lawrence, 1977; W i l l i a m s , 1974; H a r r i s & Sipay, 1975; and Mangrum, 1970). Blum et a l . ( l 9 5 9 ) r e p o r t e d 14% of s u b j e c t s t e s t e d i n 1956 were erroneously r e f e r r e d . T e c h n i c a l data 70 are l a c k i n g in the KTT manual. The MTT i s a r e l a t i v e l y new v i s i o n s c r e e n i n g measure. L i t t l e p u b l i s h e d data i s a v a i l a b l e to recommend i t s use i n a school v i s i o n s c r e e n i n g programme. Walton (1976) repo r t e d the MTT to be comparable to the MCT as a s c r e e n i n g measure (89.2% r e f e r r a l agreement). Standard Optometric Exam A consensus was obtained from the p a r t i c i p a t i n g o p t o m e t r i s t s r e g a r d i n g the v i s u a l s k i l l s assessed d u r i n g a standard optometric exam. These i n c l u d e t e s t s of o b j e c t i v e r e f r a c t i o n ( r e t i n o s c o p y ) , s u b j e c t i v e r e f r a c t i o n (myopia, hyperopia, astigmatism), t r o p i a s , p horias and f u s i o n at near and f a r p o i n t s , vergences and v e r s i o n s at f a r - and near p o i n t s , amplitude of accommodation, ste r e o a c u i t y , c o l o u r v i s i o n , and i n t e r n a l and e x t e r n a l o c u l a r h e a l t h . Subjects and Method S i x t y c h i l d r e n , aged 6-0 to 9-11, who had scheduled appointments with one of f i v e o p t o m e t r i s t s in Coquitlam, Surrey, and White Rock, B r i t i s h Columbia p a r t i c i p a t e d i n the study. A l l s u b j e c t s were given the three screening measures, a l e t t e r i d e n t i f i c a t i o n t e s t , and a standard optometric examination. Subjects wearing g l a s s e s were screened without 71 t h e i r g l a s s e s . A l e t t e r i d e n t i f i c a t i o n t e s t was given to each c h i l d p r i o r to a d m i n i s t r a t i o n of the KTT and the MTT i n order to determine whether l i m i t e d l e t t e r i d e n t i f i c a t i o n s k i l l s or v i s i o n d i f f i c u l t i e s were r e s p o n s i b l e f o r e r r o r s on MTT s u b t e s t s and the S n e l l e n . Subjects making more than two e r r o r s were excluded from the study. Each c h i l d was administered the KTT and the MTT by the r e s e a r c h e r . Subtests common to both measures were given only once; the complete KTT and remaining MTT s u b t e s t s were a l t e r n a t e d with the complete MTT and KTT s p e c i f i c s u b t e s t s . The S n e l l e n was given by the o p t o m e t r i s t s during the standard optometric exam. Commercial r e c o r d i n g forms were u t i l i z e d to record KTT and MTT performance. Summary data f o r each subject were noted on i n d i v i d u a l r ecord sheets. The r e f e r r a l c r i t e r i a given i n the d i r e c t i o n s and on the record forms were followed f o r the KTT and the MTT. For t h i s study a l l o p t o m e t r i s t s used a pas s i n g c r i t e r i o n of 20/40, f o r each eye, on the S n e l l e n . Performance on the standard optometric exam was e v a l u a t e d by the o p t o m e t r i s t ' s p r o f e s s i o n a l judgement. Subj e c t s ' performance on each s c r e e n i n g measure was compared to t h e i r performance on the standard optometric exam and c a t e g o r i z e d as a p o s i t i v e r e f e r r a l , a negative 72 r e f e r r a l , an o v e r r e f e r r a l ( f a l s e p o s i t i v e ) , or an u n d e r r e f e r r a l ( f a l s e n e g a t i v e ) . R e f e r r a l r a t e s f o r each scr e e n i n g measure were compared to r e f e r r a l s from a standard optometric exam by chi-square and phi c o e f f i c i e n t a n a l y s e s . D e l i m i t a t i o n s D e l i m i t a t i o n s centered on the sample. Subjects were c h i l d r e n aged 6-0 to 9-11 and r e g i s t e r e d i n Kindergarten through f o u r t h grade. There were few c h i l d r e n i n each age category. Only c h i l d r e n who had scheduled appointments with one of the p a r t i c i p a t i n g o p t o m e t r i s t s and whose parents agreed to t h e i r t a k i n g part i n the study were screened. Other d e l i m i t a t i o n s i n c l u d e d r e s t r i c t i n g the number of o p t o m e t r i s t s i n v o l v e d and not o b t a i n i n g i n t e r - o p t o m e t r i s t r e l i a b i l i t y because of the economic r e s t r i c t i o n s of a non- funded study and the number of v i s u a l exams allowed under h e a l t h p l a n s . L i m i t a t i o n s Within Measures As i n any t e s t , l i m i t a t i o n s e x i s t w i t h i n the three s c r e e n i n g measures which are inherent w i t h i n the measures. These i n v o l v e the complexity and completeness of d i r e c t i o n s to the examinee, the response mode r e q u i r e d , the nature of 73 the subtest s t i m u l i , and the e x p l i c i t n e s s of i n s t r u c t i o n s to the examiner regarding a d m i n i s t r a t i v e procedures and/or t e s t i n t e r p r e t a t i o n . Keystone T e l e b i n o c u l a r and M o d i f i e d T e l e b i n o c u l a r D i f f i c u l t i e s were encountered on the f o l l o w i n g KTT and MTT s u b t e s t s : 1. KTT f a r p o i n t a c u i t y (cards 4 1/2, 5, & 6) For t h i s subtest the examinee must i n d i c a t e i n which c a r d i n a l p o s i t i o n dots are l o c a t e d on receding signboards. Some c h i l d r e n , p a r t i c u l a r l y s i x and seven year o l d s , confused l e f t and r i g h t . T herefore hand gestures tended to be more r e l i a b l e than v e r b a l responses. Because the examinee must l o c a t e dots on a t o t a l of 30 signboards, on the three cards, boredom or the adoption of a response set (tendency to l o c a t e the dot i n one p o s i t i o n , e.g., on the l e f t ) may have decreased v a l i d i t y of some answers on l a t e r s ignboards. 2. MTT hyperopia (cards 4 1/2, 5, & 6) The KTT d i s t a n c e a c u i t y cards are viewed through a +2.00 lens to screen f o r hyperopia. Therefore d i f f i c u l t i e s noted f o r the KTT apply to the MTT: the l e f t - r i g h t c o n f u s i o n d i s p l a y e d i n the v e r b a l responses of young c h i l d r e n , boredom with the task, and adoption of a response s e t . Because the 74 stimulus cards are viewed through a plus l e n s , dots are not always v i s i b l e . Some c h i l d r e n had d i f f i c u l t y with the requirement that they were to look f o r something which might or might not be prese n t . T h i s task i s c o n t r a r y to most school tasks which r e q u i r e students to l o c a t e the one c o r r e c t answer. 3. KTT near p o i n t a c u i t y (cards 12, 13, & 14) Thi s subtest r e q u i r e s the examinee to i d e n t i f y d i m i n i s h i n g p a t t e r n s as being black l i n e s , black dots, or s o l i d gray presented on a yellow background. Some c h i l d r e n had d i f f i c u l t y remembering the names- for the p a t t e r n s . For example, some la r g e p a t t e r n s of black l i n e s were c a l l e d squares. Upon q u e s t i o n i n g i t was l e a r n e d that the c h i l d r e n were r e f e r r i n g to the yellow squares formed by the black l i n e s . A p o s s i b l e t o t a l of 66 p a t t e r n s c o u l d be i d e n t i f i e d on the three cards, which sometimes l e d to boredom, guessing, or a response s e t . 4. MTT f a r and near p o i n t a c u i t y (cards 4W & 12) On both cards the examinee was r e q u i r e d to i d e n t i f y rows of c a p i t a l l e t t e r s of d e c r e a s i n g s i z e . Some c h i l d r e n , p a r t i c u l a r l y the younger ones, became confused about which l i n e ( s ) they had read and which one f o l l o w e d . 75 5. c o l o u r v i s i o n (KTT & MTT cards 8 & 9) The examinee i s r e q u i r e d to read two d i g i t numbers. Some c h i l d r e n d i s p l a y e d r e v e r s a l s (e.g., reading 23 f o r 32), but c o r r e c t l y i d e n t i f i e d numerals po i n t e d out independently. 6. KTT i n t e r p r e t a t i o n D i r e c t i o n s f o r i n t e r p r e t i n g KTT subtest performance tend to be vague. Developmental f a c t o r s are noted fo r some sub t e s t s (e.g., s t e r e o p s i s , l a t e r a l posture, f u s i o n , and near p o i n t a c u i t y ) , but s p e c i f i c g u i d e l i n e s with respect to making r e f e r r a l s are not g i ven. S n e l l e n The S n e l l e n , as f r e q u e n t l y administered i n a school v i s i o n s c r e e n i n g programme, i s not without l i m i t a t i o n s . I t has a non- s t a n d a r d i z e d a d m i n i s t r a t i o n procedure and r e f e r r a l c r i t e r i o n i s at the examiner's d i s c r e t i o n . Other l i m i t a t i o n s i n c l u d e i n c o n s i s t e n t l i g h t c o n d i t i o n s , v a r i a b i l i t y i n the d i s t a n c e between the examinee and the c h a r t , and, i n school s e t t i n g s , the frequent presence of s e v e r a l c h i l d r e n in the t e s t i n g room which a f f o r d s the o p p o r t u n i t y f o r studying and/or memorizing the c h a r t p r i o r to s c r e e n i n g . 76 R e s u l t s and Conclusi o n s Chi-square and phi c o e f f i c i e n t analyses were used to make the f o l l o w i n g comparisons: 1) the r e f e r r a l e f f i c a c y of the MTT versus that of the KTT 2) the r e f e r r a l e f f i c a c y of the MTT versus that of the S n e l l e n 3) the r e f e r r a l e f f i c a c y of the KTT versus that of the S n e l l e n R e s u l t s i n d i c a t e d that there were no s i g n i f i c a n t d i f f e r e n c e s i n the r e f e r r a l e f f i c a c y of the MTT and the KTT, for any type of r e f e r r a l . The MTT was found to have g r e a t e r e f f i c a c y than the S n e l l e n f o r p o s i t i v e r e f e r r a l s and u n d e r r e f e r r a l s , X"2 ( 1 ) =7 . 000 , £ <.01 and X 2(1)=8.909, £ <.0l r e s p e c t i v e l y . No s i g n i f i c a n t d i f f e r e n c e was found between these measures f o r negative r e f e r r a l s . The S n e l l e n had gre a t e r e f f i c a c y than e i t h e r the MTT or the KTT for o v e r r e f e r r a l s , X 2 ( 1 )=7. 364, £ < . 0 1 and X 2 ( 1 ) = 5.444, £ <.05 r e s p e c t i v e l y . No other s i g n i f i c a n t r e f e r r a l d i f e r e n c e s were found between the KTT and the S n e l l e n . Not only i s i t important to know whether there are s i g n i f i c a n t d i f f e r e n c e s i n the r e f e r r a l e f f i c a c y of sc r e e n i n g measures, but a l s o f o r which type(s) of r e f e r r a l s these d i f f e r e n c e s apply. O v e r r e f e r r a l s and u n d e r r e f e r r a l s are both u n d e s i r a b l e . The former make unnecessary and t h e r e f o r e i n e f f i c i e n t use of p r o f e s s i o n a l s e r v i c e s . 7 7 U n d e r r e f e r r a l s are more s e r i o u s as r e q u i r e d p r o f e s s i o n a l a t t e n t i o n i s not obtained. T h e r e f o r e , in s e l e c t i n g a v i s i o n s c r e e n i n g measure emphasis should be pl a c e d on the measure which makes the fewest u n d e r r e f e r r a l s . The obtained r e s u l t s i n d i c a t e a s i g n i f i c a n t d i f f e r e n c e between only the MTT and the S n e l l e n f o r u n d e r r e f e r r a l s ; the MTT had the gr e a t e r e f f i c a c y . Although the S n e l l e n had gr e a t e r e f f i c a c y than e i t h e r the MTT or the KTT for o v e r r e f e r r a l s , i t s higher u n d e r r e f e r r a l r a t e decreases i t s u s e f u l n e s s as a scre e n i n g t e s t . A l s o of note i s that the MTT was more accurate than the S n e l l e n i n i d e n t i f y i n g p o s i t i v e r e f e r r a l s . The a p p r o p r i a t e n e s s of a t e s t depends upon more than i t s s t a t i s t i c a l m e r i t s . While s t a t i s t i c a l analyses d i d not show- s i g n i f i c a n t d i f f e r e n c e s between the MTT and the KTT there are a d m i n i s t r a t i v e f a c t o r s which d i f f e r e n t i a t e between them. The MTT employs l e t t e r i d e n t i f i c a t i o n s u b t e s t s to screen f a r and near p o i n t a c u i t y . Thus the s u b t e s t s ' requirements are f a m i l i a r to students. The KTT f a r po i n t a c u i t y subtest r e q u i r e s examinees to l o c a t e the p o s i t i o n of dots on receding signboards. T h i s task was found to be c o n f u s i n g . Some c h i l d r e n were not sure what was r e q u i r e d . Others d i s p l a y e d c o n f u s i o n between the l e f t and r i g h t s i d e s of the signboards and t h e r e f o r e gestures had to be used to ensure r e l i a b i l i t y of responses. The near p o i n t a c u i t y subtest on the KTT r e q u i r e s p a t t e r n i d e n t i f i c a t i o n . Some c h i l d r e n had d i f f i c u l t y remembering the c o r r e c t p a t t e r n names and whether they were to i d e n t i f y the black or yellow 78 p a r t of the p a t t e r n . Others f r e q u e n t l y l o s t t h e i r p l a c e . S e v e r a l c h i l d r e n found the n o v e l t y of t h i s subtest f r u s t r a t i n g and i t s l e n g t h and r e p e t i t i o n b o r i n g . In f a i r n e s s , not a l l MTT s u b t e s t s are f r e e of c o n f u s i o n or a d m i n i s t r a t i v e d i f f i c u l t i e s . For example, the MTT subtest for hyperopia employes the KTT f a r p o i n t a c u i t y cards and a p l u s l e n s , hence dots are not always v i s i b l e . The length, r e p e t i t i o n , and novelty of t h i s task posed d i f f i c u l t i e s f o r some c h i l d r e n . However, the o v e r a l l impression was that a d m i n i s t r a t i o n of the MTT went more smoothly, for most c h i l d r e n , than d i d the KTT. I t c o u l d be hypothesized that the l e s s f r u s t r a t i o n experienced by the examinee during s c r e e n i n g , the more r e l i a b l e h i s or her responses. T a k i n g ' i n t o c o n s i d e r a t i o n both s t a t i s t i c a l f i n d i n g s and a d m i n i s t r a t i v e d i f f e r e n c e s when s e l e c t i n g among the S n e l l e n , the KTT, and the MTT f o r use i n a school v i s i o n screening programme, the MTT appears to be the more u s e f u l measure f o r i d e n t i f y i n g students r e q u i r i n g p r o f e s s i o n a l c a r e . • Recommendations Test M o d i f i c a t i o n s M o d i f i c a t i o n to e i t h e r a d m i n i s t r a t i v e procedures or to t e s t s t i m u l i f o r p a r t s of the KTT, the MTT, and the S n e l l e n would improve screening e f f i c a c y . The f o l l o w i n g changes are 79 suggested: 1. KTT f a r p o i n t a c u i t y and MTT hyperopia (cards 4 1/2, 5, & 6) These cards be r e p l a c e d with a t e s t that would e l i m i n a t e l e f t - r i g h t d i f f e r e n t i a t i o n and would be e i t h e r s h o r t e r or more v a r i e d and t h e r e f o r e l e s s b o r i n g to young c h i l d r e n . In order to avoid- c o n f u s i o n with the terms l e f t and r i g h t c h i l d r e n be r e q u i r e d to use a p o i n t i n g response for the e x i s t i n g c a r d s . 2. KTT near p o i n t a c u i t y ' ( c a r d s 12, 13, & 14) T h i s subtest be r e p l a c e d with one that i s s h o r t e r and l e s s c o n f u s i n g to c h i l d r e n . 3. MTT a c u i t y subtests (cards 4W & 12) The rows of l e t t e r s be preceded by a numeral or geometric shape to a i d c h i l d r e n i n keeping t h e i r p l a c e . 4. KTT and MTT c o l o u r v i s i o n (cards 8 & 9) A d m i n i s t r a t i o n i n c l u d e r e t e s t i n g of f a i l u r e s due to r e v e r s a l s by having the examinee i d e n t i f y numerals i n d i v i d u a l l y r a ther than reading two d i g i t numbers. 80 5. KTT manual The manual be made more s p e c i f i c regarding i n t e r p r e t a t i o n and types of r e f e r r a l s , e s p e c i a l l y f o r primary students f o r whom developmental f a c t o r s i n f l u e n c e t e s t performance. 6 . S n e l l e n C l a r i f i c a t i o n and s t a n d a r d i z a t i o n of a d m i n i s t r a t i o n procedures are needed. a) Whether the examiner should begin with the f i r s t row and work s y s t e m a t i c a l l y through the c h a r t or whether c e r t a i n rows should be skipped i f the p r e v i o u s row was passed should be e s t a b l i s h e d . b) The number of l e t t e r s that must be c o r r e c t l y i d e n t i f i e d f o r the row to be scored as passed (e.g., 4 / 6 or 6 / 6 ) should be e s t a b l i s h e d . c) The r e f e r r a l c r i t e r i o n should be set f o r s p e c i f i c ages. d) Only the examinee should be able to see the c h a r t . Other c h i l d r e n should not be w a i t i n g where they can view i t . 81 F u r t h e r Research Given that the d i f f e r e n c e s i n r e f e r r a l e f f i c a c y obtained f o r the S n e l l e n , the KTT, and the MTT are a p p l i c a b l e only to the sample s t u d i e d , i t i s recommended that a more ext e n s i v e study of the e f f i c a c y of v i s i o n s c r e e n i n g measures, s u i t a b l e f o r use by n o n - v i s i o n s p e c i a l i s t s in a school s c r e e n i n g programme, be undertaken. I d e a l l y such a study would be a j o i n t venture by o p t o m e t r i s t s , o p h t h a l m o l o g i s t s , p u b l i c h e a l t h nurses, and school p e r s o n n e l . The f o l l o w i n g parameters are suggested: a) a randomized sample from throughout B r i t i s h Columbia b) students aged 6-0 to 18-6 be represented c) establishment of standard s c r e e n i n g r e f e r r a l c r i t e r i a d) assignment of examinees to a p a r t i c i p a t i n g o p t o m e t r i s t and/or o t h t h a l m o l o g i s t f o r p r o f e s s i o n a l e v a l u a t ion e) i n t e r - r a t e r r e l i a b i l i t y be e s t a b l i s h e d among the v i s i o n p r o f e s s i o n a l s ( i . e . , between o p t o m e t r i s t s , between o p h t h a l m o l o g i s t s , and between o p t o m e t r i s t s and o p h t h a l m o l o g i s t s ) . f) a l l screeners r e c e i v e formal t r a i n i n g i n the a d m i n i s t r a t i o n of each s c r e e n i n g measure i n v e s t i g a t e d . 82 Besides i n v e s t i g a t i n g r e f e r r a l e f f i c a c y of screening measures, such a study would provide g u i d e l i n e s f o r a sta n d a r d i z e d p r o v i n c i a l school screening programme (e.g., a l l school d i s t r i c t s use s p e c i f i e d t e s t s to screen f a r and near p o i n t a c u i t y i n set grades) and a l s o g u i d e l i n e s f o r p r o v i n c i a l r e f e r r a l c r i t e r i a . While the present study r e c o g n i z e d the need f o r such g u i d e l i n e s , i t s i n t e n t was to i d e n t i f y a r e l i a b l e s creening measure which c o u l d be used by n o n - s p e c i a l i s t s u n t i l such time as a comprehensive p r o v i n c i a l v i s i o n s c r e e n i n g programme could.be e s t a b l i s h e d . Of the three screening measures s t u d i e d the MTT had the lowest r a t e of u n d e r r e f e r r a l s . T h i s f i n d i n g recommends the MTT as a v a l i d school v i s i o n s creening measure. 83 BIBLIOGRAPHY A l l e n , M. J . (1977). The r o l e of v i s i o n i n l e a r n i n g d i s o r d e r s . J o u r n a l of Le a r n i n g D i s a b i l i t i e s , 10(7), 41 1-415. American Academy of P e d r i a t r i c s . ( 1 9 7 2 ) . The eye and l e a r n i n g d i s a b i l i t i e s . J o u r n a l of School Health, 42(4), 218. Benton, C. D. (1973). Comment: The eye and l e a r n i n g d i s a b i l i t i e s . 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Nonparametric s t a t i s t i c s f o r the b e h a v i o r a l s c i e n c e s . New York: McGraw-Hill. Soderberg, D. G. (1969). V i s i o n and school performance. Education, 89, 373-376. Spache, G. D. (1965, January 14). What's wrong with present methods of v i s u a l screening? The Optometric Weekly, 43-47. Suchoff, I. B. (1981). Research on the r e l a t i o n s h i p between reading and v i s i o n - What does i t mean? Jo u r n a l of Learning D i s a b i l i t i e s , _1_4 (10), 573-576. Taubenhaus, L. J . & Jackson, A. A. (1969). V i s i o n Screening of Preschool C h i l d r e n . S p r i n g f i e l d : C h a r l e s C. Thomas P u b l i s h e r . Vancouver General H o s p i t a l . (1979, September). L i f el'i-ne Magazine. 1(3). V e t t e r l i , C. H. (1959). How good i s 20/20 v i s i o n ? Education, 80(1), 41-45. von Noorden, G. K. (1980). B i n o c u l a r v i s i o n and o c u l a r m o t i l i t y . S t . L o u i s : The C.V. Mosby Co. Walton, H. N., Z i r h u t , M., & Armstrong, B. (1976). Comparison of v i s i o n s c r e e n i n g by the M o d i f i e d T e l e b i n o c u l a r Technique and the M o d i f i e d C l i n i c a l Technique. Paper presented at the annual meeting of the I n t e r n a t i o n a l Reading A s s o c i a t i o n , ( 2 1 s t ) , Anaheim, CA. Weintraub, S. (1973). V i s i o n - v i s u a l d i s c r i m i n a t i o n , Reading r e s e a r c h p r o f i l e s , a b i b l i l g r a p h y s e r i e s . Newark,DE: ERIC/CRIER + IRA. W i l l i a m s , R. T. (1974). V i s u a l s c reeninng: A procedure. Paper presented at the annual meeting of the Western C o l l e g e Reading A s s o c i a t i o n , ( 7 t h ) , Oakland, CA. 89 Wilson, W. K. (1969). School screening and v i s i o n d y s f u n c t i o n . In Wold, R. M. (Ed.), V i s u a l and p e r c e p t u a l aspects f o r the a c h i e v i n g and underachieving c h i l d (pp. 211-222). S e a t t l e : S p e c i a l C h i l d P u b l i c a t i o n s . Wold, R. M. (Ed.). (1978). V i s i o n i t s impact on l e a r n i n g . S e a t t l e : S p e c i a l C h i l d P u b l i c a t i o n s . Woo, G. & Bader, D. Age and i t s e f f e c t on vision_. Canadian Jo u r n a l of Optometry, 40(3&4), 29-31. APPENDIX A G l o s s a r y of V i s i o n Terms 91 GLOSSARY OF VISION TERMS Anatomical Components of V i s i o n - c r y s t a l l i n e lens - a biconvex, t r a n s p a r e n t s t r u c t u r e which, as a r e s u l t of changes in i t s c u r v a t u r e , a l t e r s the accommodative s t a t e of the eye e x t r a o c u l a r muscles - the e x t e r n a l eye muscles which c o n t r o l eye movements fovea - a 1.5 mm diameter area of the c e n t r a l r e t i n a having the h ighest r e s o l v i n g power and t h e r e f o r e maximum v i s u a l a c u i t y i n t r a o c u l a r muscles - the muscles i n s i d e the eyes which c o n t r o l p u p i l diameter and accommodation v i s u a l c ortex - that part of the b r a i n l o c a t e d i n the o c c i p i t a l area which i s i n v o l v e d with v i s u a l p e r c e p t i o n 92 V i s u a l Terms accommodation - the neuro-muscular process r e s p o n s i b l e f o r changes i n the shape of the lens which causes changes in the eye's f o c u s s i n g d i s t a n c e , t h e r e f o r e o b j e c t s at v a r y i n g d i s t a n c e s can be viewed c l e a r l y ; i s important in near p o i n t tasks (e.g., reading) amblyopia ( l a z y eye) - reduced a c u i t y not a t t r i b u t a b l e to s t r u c t u r a l or p a t h o l o g i c a l anomalies and not responsive to r e f r a c t i v e c o r r e c t i o n a n i s e i k o n i a - a r e l a t i v e d i f f e r e n c e in the s i z e and/or shape of an image i s p e r c e i v e d c o l o u r b l i n d n e s s - the i n a b i l i t y to p e r c e i v e some or a l l wave lengths of l i g h t convergence - the neuro-muscular process r e s p o n s i b l e f o r t u r n i n g the eyes inwards, when changing f i x a t i o n from f a r to near; a s s o c i a t e d with i n c r e a s e d accommodation 93 corresponding r e t i n a l p o i n t s - two r e t i n a l p o i n t s , one i n each eye, which when s t i m u l a t e d give r i s e to a s i n g l e v i s u a l percept d i p l o p i a - the c o n d i t i o n in which a lack of f u s i o n r e s u l t s in a s i n g l e o b j e c t being p e r c e i v e d as two o b j e c t s ; may not be d e t e c t e d unless the eyes are t e s t e d together divergence - the neuro-muscular process r e s p o n s i b l e f o r tu r n i n g the eyes outwards when changing f i x a t i o n from near to f a r ; a s s o c i a t e d with decreased accommodation f u s i o n - the s l i g h t l y d i f f e r e n t images seen simultaneously by each eye are fused i n t o one image i n the b r a i n ; slow f u s i o n may hinder reading motor f u s i o n - the e x t r a o c u l a r muscular process r e s u l t i n g i n the simultaneous s t i m u l a t i o n of corresponding r e t i n a l p o i n t s sensory f u s i o n - the neural process which combines and i n t e g r a t e s i n t o a s i n g l e percept the p e r c e p t u a l images which are seen s e p a r a t e l y by the two eyes 94 f i x a t ion - l o o k i n g at and b r i e f l y f o c u s i n g on an o b j e c t so that i t s image f a l l s on the fovea of the eye p u r s u i ts - f o l l o w i n g eye movements which maintain f o v e a l f i x a t i o n on a moving o b j e c t saccades - abrupt, v o l u n t a r y s h i f t s i n f i x a t i o n from one p o i n t to another, as occurs i n reading; may not be f u l l y developed u n t i l age s i x or seven p h o r i a - a l a t e n t o c u l a r d e v i a t i o n (not d e t e c t e d unless s p e c i f i c t e s t i n g done, e.g., a cover t e s t ) i n which the primary l i n e s of s i g h t f a i l to i n t e r s e c t at the o b j e c t being viewed esophoria (overconvergence) - the inward t u r n i n g of the eyes r e l a t i v e to each other t h e r e f o r e , the primary l i n e s of s i g h t over-converge exophoria (underconvergence) - the outward t u r n i n g of the eyes r e l a t i v e to each other t h e r e f o r e , the primary l i n e s of s i g h t under-converge primary l i n e of s i g h t - the l i n e j o i n i n g the fovea with the o b j e c t being viewed 95 s t e r e o p s i s (depth p e r c e p t i o n ) the b i n o c u l a r v i s u a l process which permits the judgement of r e l a t i v e d i s t a n c e s of v i s u a l o b j e c t s ; b i n o c u l a r f u s i o n i s necessary f o r s t e r e o p s i s t r o p i a (strabismus, squint) - a manifest o c u l a r d e v i a t i o n i n which the primary l i n e s of s i g h t f a i l to i n t e r s e c t at the o b j e c t being viewed due to a lack of b i n o c u l a r f i x a t i o n , which r e s u l t s from abnormal alignment (lack of muscle balance) between the eyes e s o t r o p i a (cross-eyed) - convergent strabismus; lack of f u s i o n because one eye turns i n too f a r e x o t r o p i a (walleyed) - d i v e r g e n t strabismus; lack of f u s i o n because one eye turns out too f a r v i s u a l a c u i t y - the c l e a r n e s s of v i s i o n which i s a f u n c t i o n of the sharpness of r e t i n a l focus, the s e n s i t i v i t y of the nervous system, and p e r c e p t i o n ( i n t e r p r e t a t i o n ) which occurs i n the b r a i n ametropia - a c l e a r image i s not formed due to r e f r a c t i v e e r r o r s 96 anisometropia - the r e f r a c t i v e c o n d i t i o n i n which the degree of r e f r a c t i v e e r r o r d i f f e r s between the two eyes ast igmat i sm - the r e f r a c t i v e c o n d i t i o n i n which l i g h t rays from a s i n g l e source are not focused at a s i n g l e p o i n t , but r a ther as two images at d i f f e r e n t d i s t a n c e s , o f t e n at r i g h t angles, t h e r e f o r e a d i s t o r t e d (e.g., b l u r r e d or slanted) image i s seen at both f a r and near d i s t a n c e s emmetropia - the r e f r a c t i v e c o n d i t i o n in which p a r a l l e l l i g h t rays enter the eye and focus e x a c t l y on the r e t i n a r e s u l t i n g in a c l e a r r e t i n a l image hyperopia - the r e f r a c t i v e c o n d i t i o n i n which p a r a l l e l l i g h t rays are focused behind the r e t i n a when accommodation i s r e l a x e d ; i f there i s s u f f i c i e n t accommodation to compensate d i s t a n c e o b j e c t s may be seen c l e a r l y myopia - the r e f r a c t i v e c o n d i t i o n i n which p a r a l l e l l i g h t rays are focused in f r o n t of the r e t i n a , r e s u l t i n g i n a b l u r r e d r e t i n a l image f o r o b j e c t s f u r t h e r than the near p o i n t 97 V i s i o n Personnel ophthalmologist - a medical p r a c t i o n e r s p e c i a l i z i n g in the medical and s u r g i c a l care of the eyes who diagnoses and t r e a t s s t r u c t u r e s and f u n c t i o n s of the eye, d i s e a s e s of the eye, p r e s c r i b e s c o r r e c t i v e lenses ( g l a s s e s ) , contact l e n s e s , medications, and performs surgery; provides s p e c i a l i z e d (secondary) v i s i o n c a r e opt i c ian - a person who f i l l s p r e s c r i p t i o n s , from an ophthalmologist or an o p t o m e t r i s t , f o r c o r r e c t i v e or contact l e n s e s o p t o m e t r i st - a nonmedical p r a c t i o n e r t r a i n e d to diagnose s t r u c t u r e s and f u n c t i o n s of the eyes ( r e f r a c t i v e e r r o r s , b i n o c u l a r anomalies, d i s e a s e s of the eyes), and to p r e s c r i b e c o r r e c t i v e l e n s e s ( g l a s s e s ) , contact l e n s e s , o p t i c a l a i d s , and v i s i o n therapy; u s u a l l y p r o v i d e s an i n d i v i d u a l with primary v i s i o n care 98 o r t h o p t i s t - an i n d i v i d u a l who a d m i n i s t e r s v i s u a l p e r c e p t u a l and c o o r d i n a t i o n (eye muscle) t r a i n i n g to enhance b i n o c u l a r v i s i o n , under the d i r e c t i o n of an optometrist, or ophthalmologist Other V i s i o n Terms Landolt r i n g or Landolt broken c i r c l e t e s t - a c h a r t of c i r c l e s with openings in d i f f e r e n t p o s i t i o n s ; dimensions of r i n g and opening are r i g i d l y p r e s c r i b e d and t h e r e f o r e t h i s t e s t overcomes the l e t t e r s i z e v a r i a t i o n s found among manufacturers of S n e l l e n c h a r t s prism d i o p t e r - a metric u n i t d e s c r i b i n g the amount of d e v i a t i o n i n c o o r d i n a t i o n or b i n o c u l a r v i s i o n r e s o l u t i o n a c u i t y - i n v o l v e s the r e l a t i o n s h i p of the s t i m u l u s and i t s background; part of the background shows through openings in the s t i m u l u s , hence the stimulus i s viewed as a separate o b j e c t from the background 99 Note. Recognition and a p p r e c i a t i o n are due the p a r t i c i p a t i n g o p t o m e t r i s t s f o r t h e i r a s s i s t a n c e in p r e p a r i n g t h i s g l o s s a r y , e s p e c i a l l y Drs. Jackson, J a n t z i , and Smith f o r p r o v i d i n g the more t e c h n i c a l d e f i n i t i o n s . APPENDIX B The M o d i f i e d C l i n i c Technique 101 THE MODIFIED CLINIC TECHNIQUE The M o d i f i e d C l i n i c Technique (MCT) employs a s e r i e s of t e s t s to screen f o r the presence and extent of v i s u a l anomalies. T e s t s screen f o r o b j e c t i v e r e f r a c t i o n ( r e t i n o s c o p y ) , s u b j e c t i v e r e f r a c t i v e s t a t u s (myopia, hyperopia, astigmatism) at f a r p o i n t and reading d i s t a n c e s , muscle ' imbalance (cover t e s t ) , amblyopia, and anisom e t r o p i a . Colour v i s i o n and stereo a c u i t y t e s t s may be adm i n i s t e r e d . I n t e r n a l and e x t e r n a l o c u l a r h e a l t h i s a l s o noted. The i n c l u s i o n of the cover t e s t and r e t i n o s c o p y n e c e s s i t a t e s the MCT be administered by p r o f e s s i o n a l v i s i o n care p e r s o n n e l . 102 APPEND IX C The O r i n d a S t u d y 1 03 THE ORINDA STUDY ( V i s i o n Screening f o r Elementary Schools) H.L.Blum, H.B.Peters, J.W.Bettman, 1959 The Orinda study i n v e s t i g a t e d the r e f e r r a l e f f i c a c y of s e v e r a l v i s i o n s c r e e n i n g procedures among school students i n Orinda, C a l i f o r n i a , a r e s i d e n t i a l suburban community. The study began in 1954 with students i n grades one through s i x being t e s t e d . Students were rescreened i n 1955 and 1956. The number of p a r t i c i p a n t s v a r i e d over the three years of the study and r e f l e c t s changes w i t h i n the school p o p u l a t i o n . The f o l l o w i n g t a b l e s d e s c r i b e the sample, l i s t the v i s u a l s k i l l s screened, and show the obtained r e s u l t s . Only i n f o r m a t i o n p e r t i n e n t to the present study i s presented. T a b l e X I I S u b j e c t s T e s t e d a n d V i s i o n S c r e e n i n g T e s t s A d m i n i s t e r e d E a c h Y e a r d u r i n g t h e O r i n d a S t u d y C a 1 i f o r n i a S t a t e R e c o m m e n d e d P r o c e d u r e p a r e n t o b s e r v a t i o n s c 1 i n i c a 1 y e a r N a g e s g r a d e s q u e s t i o n n a i r e t e a c h e r n u r s e 5 n e 1 1 e n p 1 u s 1 e n s c o v e r t e s t M V T 1 K T T ' M C T 1 e x a m 1 9 5 4 1 1 6 3 5 - 1 3 1 - 6 X X X X X X X X X 1 9 5 5 1 4 7 5 6 - 1 4 1 - 7 X X X X X " X X 1 9 5 6 1 2 7 4 7 - 1 5 3 - 8 X X X X X X X 5 X X N o t e . S u m m a r i z e d f r o m B i u r n e t a l . ( 1 9 5 9 ) ' M a s s a c h u s e t t s V i s i o n T e s t ' K e y s t o n e T e l e b i n o c u l a r T e c h n i q u e ' M o d i f i e d C l i n i c T e c h n i q u e ' n o r e t e s t i n g o f f a i l u r e s a s r e c o m m e n d e d b y m a n u f a c t u r e r ' r e t e s t i n g o f f a i l u r e s c o n d u c t e d b-f o 1 05 Table XIII Keystone T e l e b i n o c u l a r Subtests Administered duri n g the Orinda Study i n 1955 and 1956 v i s u a l s k i l l year 1955 1956 simultaneous v i s i o n X X l a t e r a l p h o r i a ( f a r & near) X X f u s i o n ( f a r & near) X X l e f t v i s u a l a c u i t y ( f a r & near) X X r i g h t v i s u a l a c u i t y ( f a r & near) X X s t e r e o p s i s - x v i s u a l a c u i t y , both eyes ( f a r & near) c o l o u r p e r c e p t i o n Note. Summarized from Blum et a l . (1959) 1 06 Table XIV Percentage of R e f e r r a l s , by R e f e r r a l Category, in the Orinda Study dur i n g 1955 and 1956 REFERRAL CATEGORIES c o r r e c t r e f e r r a l s non r e f e r r a l s over r e f e r r a l s under r e f e r r a l s SCREENING MEASURES C l i n i c a l 1 955 1 956 Exam 1 7% 1 7% 83% 83% KTT 1 1 955 1 956 MCT 2 1 955 1 956 1 6% 9% 1 7% 1 7% 27% 77% 81% 82% 56% 3 6% 2% 1% 1% 8% <. 5% <.5% Note. Summarized from Blum et a l . (1959) 1 Keystone T e l e b i n o c u l a r Technique 2 M o d i f i e d C l i n i c Technique 3due to examiner e r r o r 1 07 Table XV Percentage of Primary Student R e f e r r a l s , by R e f e r r a l Category, i n the Orinda Study d u r i n g 1955 1 and 1956 2 REFERRAL CATEGORIES c o r r e c t non over under r e f e r r a l s r e f e r r a l s r e f e r r a l s r e f e r r a l s SCREENING MEASURE C l i n i c a l 1955 1956 KTT 3 1 955 1 956 MCT 4 1 955 1 956 Exam 16% 1 8 % 1 5% 9% 1 5% 1 8% 84% 82% 23% 76% 83% 79% 61% ! 6% 1% 3% 1% 9% 1% <.5% Note. Summarized from Blum et a l 1 students aged 6-8 years 2 s t u d e n t s aged 7-9 years 3Keystone T e l e b i n o c u l a r Technique "Modified C l i n i c Technique 5due to examiner e r r o r (1959) APPENDIX D Recording Forms and P r o t o c o l s COMPARISON OF THREE VISION SCREENING MEASURES WITH A STANDARD OPTOMETRIC EXAM SUBJECT: DATE: SEX: M F D.O.B, GRADE: C A . TIME: s t a r t e d stopped t o t a l TEST PERFORMANCE: LETTER IDENTIFICATION: /26 c r i t e r i a met ( c r i t e r i a - 24/26, 92%) c r i t e r i a not met KEYSTONE TELEBINOCULAR TECHNIQUE: 1st a d m i n i s t r a t i o n r e t e s t no r e f e r r a l i n d i c a t e d r e f e r r a l i n d i c a t e d r e t e s t MODIFIED TELEBINOCULAR TECHNIQUE: 1st a d m i n i s t r a t i o n r e t e s t no r e f e r r a l i n d i c a t e d r e f e r r a l i n d i c a t e d r e t e s t SNELLEN: no r e f e r r a l i n d i c a t e d r e f e r r a l i n d i c a t e d OPTOMETRIC EXAMINATION: unnecessary r e f e r r a l " necessary r e f e r r a l ( c o r r e c t i v e l e n s e s , therapy, continued o b s e r v a t i o n ) COMMENTS: LETTER IDENTIFICATION TEST T P G A F S D E L W K V C z R 0 H J B I N Y U M X Q School Vision Screening FOR USE WITH THE KEYSTONE TELEBINOCULAR SCHOOL SURVEY CUMULATIVE RECORD FORM NO. 5-/1 CATALOG ORDER NO. 5527 R A P I D V I S I O N S C R E E N I N G T E S T S DISTANT VISION TESTS Pass Fail 1A. Dog should be seen jumping over pig The 4 blocks should be seen merged into 3 2A. Balloon No. 2 is farthest away I Balloon No. 5 is closest > Balloon 2 is red; balloon 5 Is green Letters in Block A: DCZPT (Trainingonly) Letters in Block B: Z P D T C * Letters in Block C: L D T C Z * NEAR VISION TESTS (16 INCHES) 3A. Yellow line should pass through white square The 4 balls should be seen merged into 3 4A. Letters in Block A: L O Z P C (Trainingonly) Letters in Block B: T Z O D L * Letters in Block C: O P T D C * * Passing score: at least 4 letters Failure on any test above indicates need for full test at right. C O M P R E H E N S I V E T E S T B A T T E R Y : Q U E S T I O N S 1. What do you see? 2. Does the yellow line go through, above, or below the red ball? 3. To what number, or between what numbers, does the arrow point? 4. How many balls do you see? 4V2.ln each signboard there are five diamonds (point). In one dia- mond is a dot. (point to first signboard, show dot in the left diamond.) Ask: Where is the dot in Nos. 2, 3, 4, 5, etc.? Tests 5 and 6 are the same as No. 4'A. Ask: Where is the dot? 7. (Point to the top line of symbols and name each one. Show by pointing that the cross stands out in 3-D.) Ask: Which symbol stands out in each of the next lines? 8. What number is in the upper circle? The lower left? The lower right? {Test 9 is the same as Test 8.) 10. To what number, or between what numbers, does the arrow point? 11. How many balls do you see? 12. In the three circles in the center (point) you see black crossed lines, black dots, and solid gray. Starting with No. 1 of the outer circles, you see black dots. No. 2 has black lines. What do you see in No. 3? Go as far as you can. Tests 13 and 14 are the same as 12: Name what you see in each of the circles. Revised 1974 bv Kevstone V i e w 73-6561 Wearing glasses? Yes: For reading only. for distance only ; both No. Snellen Standard (if desired) With glasses: RE LE Without glasses: RE LE TEST LEFT EYE ONLY RIGHT EYE ONLY UNSATISFACTORY Underconvergence and/or low usable vision RE- TEST AREA EXPECTED RESPONSE RE- TEST AREA UNSATISFACTORY Overconvergence FA R P OI NT  TE ST S | 1 (DB-10A) Simultaneous Vision FA R P OI NT  TE ST S | 2 (DB-ao Vertical Posture 0 on fy o ? 0 2 O ; ft 3 o ? O 2 ft 3 • 3 * 2 D 3 * 2 O 3 o » m •« «• 2 0 ° FA R P OI NT  TE ST S | onty u? O 2 ft 3 FA R P OI NT  TE ST S | 3 (DB-9) Lateral Posture Arrow only Numbers only 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 FA R P OI NT  TE ST S | 4 (DB-4K) Fusion only CD • • CD only 0 Far apart CD CD • 0 Close CD CD • • CD • Close 0 CD CD • Far apart 0 CD CD • FA R P OI NT  TE ST S | 4/2 (DB-1D) Usable Vision, Both Eyes 1 L 49% 2 B 70% 3 T 84% 4 L 88% 5 R 92% 6 T 96% 7 L 98% 8 B 100% 9 B 103% 10 R 105% FA R P OI NT  TE ST S | 5 (DB-3D) Usable Vision, Right Eye No Dots Sen Untesa Lei Eye ' ts Ocdudea 1 T 49% 2 R 70% . 3 L • 84% 4 T 5 B 92% 6 B 96% 7 L 98% 8 R 100% 9 T 103% 10 R 105% FA R P OI NT  TE ST S | 6 (DB-2D) Usable Vision, Left Eye No Dots Sen Unles R>Bhi Eye Is Ocluded 1 B 49% 2 L 70% 3 R 84% 4 R 88% 5 T 92% 6 L 96% 7 B 98% 8 L 100% 9 R 103% 10 T 105% FA R P OI NT  TE ST S | 7(DB-6D) Stereopsis u 4. only u only » + O 0 • • O * + O FA R P OI NT  TE ST S | 8 (DB-13A) Color Perception Top 32 Le 7 ft 9 Right 23 NONE CORRECT 1 Out of 3 2 Out of 3 ALL CORRECT FA R P OI NT  TE ST S | 9(DB-14A) Color Perception Top 63 Left 92 Bight 56 NONE CORRECT 1 Out of 3 2 Out o l 3 ALL CORRECT | NE AR  PO IN T T ES TS  | 10 (DB-9B) Lateral Posture Arro only ti Nur c nbers nly 10 9 8 7 6 5 4 3 • 2 | NE AR  PO IN T T ES TS  | 11 (DB-5K) Fusion CD • • CD only 0 Far apart CD CD • 0 Close CD CD • • CD • Close 0 CD CD • Far:apart 0 CD̂  CD • | NE AR  PO IN T T ES TS  | 12 (DB-15) Usable Vision, Both Eyes 1 D 10% 2 L 20% 3 D 30% 4 D 40% 5 L 6 D 50% 7 D 60% 8 50% 9 D 70% 10 D 70% 11 G 80% 12 L .80% 13 L 90% 14 D 90% 15 L 100% 16 D 100% 17 L 102% 18 D 102% 19 G 103% 20 D 03% 21 D 105% 22 L 105% | NE AR  PO IN T T ES TS  | 13 (DB-16) Usable Vision, Right Eye 1 : D 10% 2 D 20% 3 L 4 D 40% L 50% 6 D 50% 7 D 60% 8 L 60% 9 D 70% 10 L 70% 11. D 80% 12 G 13 L 90% 14 L 90% 15 D 100% 16 D 100% 17 G 102% 18 D 102% 19 L 103% 20 D 03% 21 D 105% 22 L 105% | NE AR  PO IN T T ES TS  | 14 (DB-17) Usable Vision, Left Eye 1 L 10% 2 D 20% 3 D 30% 4' 0 40% 5 L 50% 6 0 50% 7 L 60% 8 D SO% 9 0 70% 10 D 70% 11 L 60% 12 L 80% 13 G 90% 14 D 90% 15 L 100% 16 D 100% 17 L 102% 18 0 102% 19 L 103% 20 G 03% 21 0 105% 22 L 105% Examined by: Name Sex, School City Grade IRoom Teacher Date of birth Date of test 112 Test Record Form WT Walton Modified Telebinocular Technique of Vision Screening KEYSTONE VIEW Name _ School- Grade— Age _ Complaints Room_ District— Teacher_ Date this test. Glasses worn? • Reading only D Distance only D All times D N O TEST LEFT EYE ONLY RIGHT EYE ONLY 'arTolnn'osition UNSATISFACTORY Underconvergence, left eye turns up- ward, myopia, and/or astigmatism BORDER-LINE EXPECTED RESPONSE BORDER-LINE UNSATISFACTORY Overconvergence, right eye turns up- ward, and/or hyperopia Place Card Holder at Simultane- ous vision 2 Vertical phoria Line only Symbols Only O o -QL o i 3 Lateral phoria Arrow only Numbers only 1 5 14 1 3 12 11 10 1 4 Fusion Only CD © Only # Far apart © CD Close CD Four becoming three CD Three becoming four Close # CD CD 4W A cuity, astigmatism, myopia and amblyopia Upper group: Right eye Lower group: Left eye NWM D G 0 UZV C F P E 20/70 20/50 ZWN EDP VMU QFOC 20/70 20/50 PGB OECF 20/40 BOF CPDE 20/30 CBDEGPO 20/25 FCE OBGP 20/40 EDP CFOB 20/30 OPGEDBC 20/25 FBDPGEC 20/20 CEGPDBF 20/20 Far apart # CD CD Insert plus lens 4)4 Hyperopia, both eyes Use 2.00 D plus lens Hyperopia, right eye Use 2.00 D plus lens Hyperopia, lelt eye Use 2.00 D plus lens Remove plus lens 7 Stereopsis L°l T o p 32 Left 79 Right 23 T o p 63 Left 92 Right 56 o -A- o • • 2 3 4 5 6 7 o 12 Color vision None correct 1 out of 3 2 of 3 All correct 9 Color vision None correct 1 out of 3 2 of 3 All correct |  N E A R  P O IN T  T E ST S |  10 Lateral phoria Arrow only Numbers only 10 9 8 7 6 5 4 3 2 |  N E A R  P O IN T  T E ST S |  11 Fusion Only CD • • © Only 9 Far apart © CD • • Close CD CD • Four becoming three • CD • Three becoming four Close # © © • Far apart # © ® • |  N E A R  P O IN T  T E ST S |  12 Acuity, presbyopia, reduced Column A: Left eye Ft 20/200 DCV 20/100 VC ZRS 20/70 vz NOS 20/50 DS CHV 20/40 zo NSH 20/30 D V C N Z O R 20/20 |  N E A R  P O IN T  T E ST S |  accommo- dation, and high ACA Column B: Right eye D 20/200 SHR 20/100 HO NCZ 20/70 DC RHV 20/50 ZN ORD 20/40 CN ZOR 20/30 V N S C H O D 20/20 |  N E A R  P O IN T  T E ST S |  Column C: Both eyes S 20/200 NOZ 20/100 ZD SVR 20/70 l i e 20/50 VZ ONS 20/40 RS DCV 20/30 S D C V N O Z 20/20 tj Copyright 1981 by Mast/Keystone, Davenport, IA Printed in U.S.A. (73-7161) Ordering Number 5 5 4 6 Examined by Passed O Recommend professional examination THE MODIFIED VISUAL SKILLS TEST FOR USE WITH THE TELEBINOCULAR GENERAL INSTRUCTIONS The Modified Telebinocular test procedure is based on the standard f i f t e e n card s k i l l s set with two cards added and three temporarily deleted. Insert the new 4-W (Walton) card between the #4 and #4i test cards. Remove test cards #12., #13 and #14, and insert the Sloan Near Point Acuity Card to replace them. Administer a l l tests per standard procedures except for cards #4W, #4 1/2, #5 and #6. See following special instructions. INSTRUCTIONS FOR #4-W CARD This test screens for the following conditions: Amblyopia, anisometropia, near-sightedness and astigmatism (also far-sightedness combined with astigmatism and near-sightedness combined with astigmatism.) \ Present tht test card binocularly, i n i t i a l l y . Ask, "What do you see?" . Answer shoui be: "two groups of l e t t e r s . " Ask, "Are they equally clear?" If ,iot in i some t rop i a , amblyopia or suppression is indicated. Begin with the . ;r nroup of letters (right eye) and direct the subject to start the top line and read down. Follow them on the record form tes' • '-ing each error. Stop them when they make four errors on o.ie l i n e . Repeat with the lower group of letters ( l e f t eye). If ti.e subject is confused by the presence of both groups of l e t t e r s , the test may be perforn -d by occluding the l e f t eye and then the right eye. Opt i onaI After the i n i t i a l binocular test, you may simply repeat under monocular conditions ( l e f t eye then right eye occluded) for additional information. Different results from the binocular test should be recorded. Note: The 20-70 line is non-astigmatic and is included to allow the average person to achieve some success before proceeding to the actual t-^st material. SPECIAL INSTRUCTIONS FOR ADMINISTERING THE #4 1/2, #5, and #6 TEST CARDS Explanat i on: This test is for far-sightedness. It is a Binocular Plus Lens Test. The targets provide enough stereoscopic clues to assure a relaxed test environment. TEST card #4 1/2 serves the dual purpose of allowing a moment of relaxation in the instrument prior to actually administering the tests on cards #5 and #6, and at the same time allows the instructions to be given for taking the test with the test clues available to both eyes, thus circumventing any problems created by a mon.o.cuj.a.r. .(one.-eyed) visual condition. Administration: Insert the Plus Lens into the instrument or place appropriate spectacles on person being tested and expose the #4 1/2 test card. Keystone View, Division of Mast/Keystone Ask the question, "Do you see the railroad tracks goin-- i the bridge into the distance?" Continue, "Under the number one i •> signboard with five diamonds in i t . A black dot might be in one of them. "Do you see a black dot in either the top, bottom, l e f t , right or middle diamond?" If no dot is reported proceed to test #5. If the dot is correctly i d e n t i f i e d have them locate dots successively in each signboard as far as possible. Record last correct response with a v e r t i c a l divider line to i t s right. Proceed to test #5. Test #5: Start at #1 signboard and record last correct response as above. Test #6: Identical to test #5, except for the eye tested. Remove Plus Lens. Proceed to Tests #7, #8, #9, #10, and #11, and ..dmlnlster per standard procedures. Test #12: Ask the patient, "How many columns do you see?" If 3 are reported, have patient read columns A, B and C. If 4 or more columns are reported, occlude the right eye and have patient read column A. Then occlude the l e f t eye and have patient read column B. (Disre- gard column C.) This completes the test. Referral is based upon f a i l u r e to correctly identify 3 or more 20/40 lette r s in columns A, B or C. (Col- umn C is only used i f 3 columns are observed.) INTERPRETATION AND REFERRAL CRITERIA Test #1 - Failure to see both targets indicates either enucleated eye, blindness in one eye, a gross suppression or a markedly deviating eye. - - R e f e i — Proceed with following tests where feasible. Test #2 - Failure indicates an incorrect v e r t i c a l posture of one eye re- lative to the other. -- Refer -- Test #3 and #4 - Evaluate together -- f a i l u r e on #3 and #4 -- Refer -- Failure on 3 or 4 on 1 y -- Refer to teacher for close c 1 a s s tv.-: < observation. Refer on classroom symptoms i f found. Tests 4-W - Primary grades -- Refer when they f a i l to read four or more letters on the 20/40 line. (Refer upper elementary grades i f they f a i l four or more on the 20/30 line.) Test #4 1/2 - No referral - See manual for evaluation. Tests #5 and #6 - Refer unsatisfactory responses (7 thru 10.) Test #7 - (Stereopsis) - Administer to a l l age groups. Failure below 3rd grade refer to teacher for classroom observation and evaluation. 3rd grade and up refer only i f associated with a f a i l u r e on one or more of the other tests (3 6 4; 10 & 11 evaluated together) or i f no correct responses. Tests #8 and #9 - Color tests. No referral. Advise teacher and parents. Tests #10 and #11 - Same c r i t e r i a as tests #3 and #4. Test #12 - Refer when they f a i l to correctly identify three or more letters in the 20/40 column. East 12th Street Davenport, IA 52803 APPEND IX E The CA, S e x , and G r a d e o f S u b j e c t s 1 1 4 Table XVI C l a s s i f i c a t i o n of Subjects by Age and Sex SEX males females AGE t o t a l per age 6- 0 to 6-11 3 8 11 7- 0 to 7-11 6 15 21 8- 0 to 8-11 10 8 18 9- 0 to 9-11 16 4 10 Table XVII C l a s s i f i c a t i o n of Subjects by Age and Grade GRADE kinder g a r t e n one two three four • AGE 6- 0 to 6-11 2 8 1 7- 0 to 7-11 9 11 1 8- 0 to 8-11 1 6 10 1 9- 0 to 9-1 1 6 4 t o t a l per grade 2 18 18 17 5 Note. N=60

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