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Focussing both eyes on health outcomes: revisiting cataract surgery Davis, Jennifer C; McNeill, Heather; Wasdell, Michael; Chunick, Susan; Bryan, Stirling Sep 3, 2012

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RESEARCH ARTICLE Open AccessFocussing both eyes on health outcomes:revisiting cataract surgeryJennifer C Davis1,2*, Heather McNeill3, Michael Wasdell3, Susan Chunick3 and Stirling Bryan1,2AbstractBackground: The appropriateness of cataract surgery procedures has been questioned, the suggestion being thatthe surgery is sometimes undertaken too early in the disease progression. Our three study questions were: What isthe level of visual impairment in patients scheduled for cataract surgery? What is the improvement followingsurgery? Given the thresholds for a minimal detectable change (MDC) and a minimal clinically important difference(MCID), do gains in visual function reach the MDC and MCID thresholds?Methods: The sample included a prospective cohort of cataract surgery patients from four Fraser Health Authorityophthalmologists. Visual function (VF-14) was assessed pre-operatively and at seven weeks post-operatively. Twogroups from this cohort were included in this analysis: ‘all first eyes’ (cataract extraction on first eye) and ‘both eyes’(cataract removed from both eyes). Descriptive statistics, change scores for VF-14 for each eye group andproportion of patients who reach the MDC and MCID are reported.Results: One hundred and forty-two patients are included in the ‘all first eyes’ analyses and 55 in the ‘both eyes’analyses. The mean pre-operative VF-14 score for the ‘all first eyes‘ group was 86.7 (on a 0–100 scale where 100 is fullvisual function). The mean change in VF-14 for the ‘both eyes‘ group was 7.5. Twenty-three percent of patientsachieved improvements in visual function beyond the MCID threshold and 35% saw improvement beyond the MDC.Conclusions: Neither threshold level for MDC or MCID for the VF-14 scale was achieved for a majority of patients.A plausible explanation for this is the very high levels of pre-operative visual functioning.Keywords: Cataract surgery, Visual function, Health outcomesBackgroundThe development of age-related cataracts is an inevitablepart of ageing for many people and without effectivetreatment it is one of the leading causes of blindnessworldwide [1]. The widely acknowledged standard ofcare is cataract extraction, typically performed first inthe lowest functioning eye. Compelling research evi-dence supports the efficacy and cost-effectiveness ofcataract extraction when performed in patients withpoor baseline visual acuity [2-4]. Hence, it is not surpris-ing that cataract removal, a 19-minute ambulatory sur-gery [5], is one of the most frequently performedsurgical procedures in the developed world [6].However, the appropriateness of some cataract surgeryprocedures has been questioned repeatedly, the sugges-tion being that the surgery is sometimes undertaken attoo early a stage in the disease progression [7-9]. Thisconcern is based on reports of wide variations in post-surgery outcomes and estimates of health gain [10]. Lowthresholds for cataract surgery in a Canadian setting weredemonstrated by Wright et al. in their Regional Evalu-ation of Surgical Indications and Outcomes (RESIO)study [11]. Thirty-two percent of RESIO patients sched-uled for first cataract surgery had a pre-operative visualfunction score of 90 or higher on the visual functioningVF-14 scale (where 100 is full visual functioning). Withsuch high levels of visual function, the scope forimprovements in functioning is very limited. Therefore,some 10 years after publication of the RESIO data, we re-visit cataract surgery thresholds and outcomes inCanada. Black and colleagues conducted a study in the* Correspondence: Jennifer.davis@ubc.ca1Centre for Clinical Epidemiology & Evaluation, Vancouver Coastal HealthResearch Institute, Vancouver, Canada2School of Population and Public Health, Centre for Clinical Epidemiologyand Evaluation VCH Research Institute, The University of British Columbia,Vancouver, CanadaFull list of author information is available at the end of the article© 2012 Davis et al.; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the CreativeCommons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, andreproduction in any medium, provided the original work is properly cited.Davis et al. BMC Geriatrics 2012, 12:50http://www.biomedcentral.com/1471-2318/12/50UK that ascertained whether there was overutilization ofcataract surgery in England [12]. Although the notablereduction in the visual function threshold for cataractsurgery was due to improvements in the provision ofcataract surgery, methodological challenges in measuringpost surgical outcomes rendered it impossible to con-clude whether overutilization was indeed occurring [12].To our knowledge, there is no such recent work con-ducted in Canada. As such, this study seeks to explorevisual impairment thresholds for cataract surgery andlevels of improvement seen following cataract surgery inCanada. Further, we explore factors relating to variationin thresholds and outcomes relating to cataract surgerysuch as the unit of analysis.This paper reports data collected for an evaluation ofcataract surgery outcomes conducted at Fraser HealthAuthority ophthalmology practices in British Columbiabetween April 2009 and March 2010. Supplementaryfunding to Fraser Health Authority for an expansion ofcataract surgery services is the context for the analysisreported in this paper. As the data were collected for theservice evaluation of cataract surgery outcomes, thisstudy did not require ethical review by the Fraser HealthAuthority Research Ethics Board.The primary study questions are:1What level of visual impairment was seen in patientsscheduled for cataract surgery?2What level of improvement in visual function wasseen following cataract surgery?On the latter issue, most previous work, including theRESIO study, assessed either the visual functioning gainsafter first eye surgery only [11] or after second eye sur-gery only [13,14]. The work reported here takes the viewthat cataract surgery should be defined as treatment ofthe person (i.e. surgery on both eyes) and not a singleeye, given that sight in both eyes is important for health-related quality of life.Recently, VF-14 thresholds for a minimal detectablechange (MDC) and a minimal clinically important differ-ence (MCID) were established [15]. MDC is the thresh-old for distinguishing between actual change andmeasurement error, estimated to be 10.81 on the VF-14scale [15,16]. MCID is the threshold that indicates theminimum change in score necessary for a patient to ex-perience a clinically important improvement, estimatedas 15.57 for VF-14 [15,16]. Given these new thresholds,our third study question is:3 Did gains in visual function following cataract surgeryreach the MDC and MCID thresholds, and what arethe implications of these thresholds for clinicalpractice in Canada?MethodsStudy design and sampleData were collected on a population-based prospectivecohort of ophthalmology patients listed for cataract sur-gery in the Fraser Health Authority in British Columbiabetween April 1, 2009 and March 31, 2010. The study de-sign was a non-experimental pre-post-test design. Datawere collected before surgery and at seven weeks post-cataract surgery to allow pre-operative visual functionand visual acuity to be described and variation in patientoutcomes to be explored. Figure 1 illustrates the distribu-tion of the patient sample from which the data for thispaper have been derived. Only 35 patients (8%) activelyrefused to take part in the evaluation. Within the studyperiod, 87 patients received surgery on their first eye onlyand 55 had cataracts removed from both eyes.MeasurementsAt baseline, data were collected on: Visual function (VF-14) [17] Best corrected visual acuity (Snellen Fractions) [18] Clinical variables: glare, ocular comorbidities, eyesurgery (first, second or both eyes) Indications for surgery (i.e., ‘significant cataract’,‘needs better vision’ and ‘other medical indication’) Age and sexBased on clinical considerations regarding the degreeof severity of visual impairment, three Snellen visualacuity categories were used to reflect the visual acuityreported by the ophthalmologist: ≤0.1 (lowest acuity);0.2 – 0.4; and ≥0.5 (highest acuity) [18].At follow-up (seven weeks), data were collected on vis-ual function using the VF-14.The primary outcome measure for this analysis is theVF-14, a valid and reliable 14-item instrument used toassess functional impairment related to vision in botheyes [17,19]. Each item has four possible responses. Thequestionnaire asks about ability to perform activities ofdaily living including day and night-time driving, readingsmall print or traffic signs and engaging in recreationalactivities. The instrument’s scale ranges from 0 (worst,unable to do all activities) to 100 (best, able to all activ-ities without difficulty).Statistical analysisAnalysis for question 1 (What level of visual impairmentwas seen pre-operatively in patients scheduled for cata-ract surgery?)All patients listed for their first cataract surgery weregrouped together into an ‘all first eye’ cohort (n = 142;see Figure 1). This includes patients who only had onesurgery in the study period (n = 87) and those who hadDavis et al. BMC Geriatrics 2012, 12:50 Page 2 of 8http://www.biomedcentral.com/1471-2318/12/50cataracts removed from both eyes within the study win-dow (n = 55). For all variables collected at baseline, de-scriptive statistics were calculated.Analysis for question 2 (What level of improvement invisual function was seen following cataract surgery?)Given the focus on the person rather than the eye, thisanalysis includes only patients who received surgery forboth their first and second eye within the study period(‘both eyes’, n = 55). Descriptive statistics were calculatedfor the post-operative VF-14, and for the change in VF-14 scores (week 7 score minus baseline score).Analysis for question 3 (Did gains in visual functionfollowing cataract surgery reach the MDC and MCIDthresholds?)Estimates were made of the proportion of patientsachieving the respective MDC and MCID thresholdlevels of 10.81 and 15.57. Given that this analysis is con-cerned with the change in VF-14, the sample used forthis analysis includes only patients who received surgeryfor both their first and second eye within our data col-lection time frame (‘both eyes’, n = 55).At follow-up, not all patients in the ‘both eyes’ cohorthad ‘corrected’ vision – some required new reading and/or distance glasses but had not acquired them at follow-up. A sub-group of the ‘both eyes’ cohort was establishedcomprising only those with corrected vision (n = 23).The MDC and MCID thresholds were applied to thissub-group.Unable to participate (n=460): - Declined (n=35) - Surgery cancelled (n=7) - Non-responder (n=341) - Unable to complete survey due to language or comprehension difficulty (n=77) Cataract surgery on first eye only during study period (n=87) Patients who agreed to participate (n=360) - Missing eye classification for group allocation (n=14) Cataract surgery on both eyes during study period (n=55) Cataract surgery on second eye only during study period (n=204) Analysis cohort: ‘All first eye’ (n=142) Analysis cohort: ‘Both eyes’ (n=55) )55=n()78=n( (n=55) Total number of patients approached for inclusion in study (n=820) Figure 1 Flow of study subjects.Davis et al. BMC Geriatrics 2012, 12:50 Page 3 of 8http://www.biomedcentral.com/1471-2318/12/50ResultsSampleTable 1 details the characteristics of participants for bothanalysis cohorts (‘all first eyes’ and ‘both eyes’). Patientsranged in age from 45 to 94 years, with a mean age of73, and the majority were female.Baseline visual impairment levelsBaseline data on best corrected visual acuity for the ‘allfirst eye’ group spanned the entire range with 34.5%scoring 0.5 or better, 56.3% scoring between 0.2 and 0.4and 90.8% scoring 0.2 or better (Table 1). The pre-operative VF-14 scores for the ‘all first eye’ sample areshown in Figure 2. The mean pre-operative VF-14 scorewas 86.7 (median: 90.9; interquartile range: 14.6). Ahighly skewed baseline VF-14 distribution is revealedwith the vast majority of patients having a score of 80 orhigher (on the 0–100 scale). For the ‘both eyes’ group,most patients (74.5%) had better baseline visual acuity intheir second eye (Table 1).In order to provide a reference point, comparison wasmade of these new data with those reported by theRESIO investigators a decade earlier (Figure 3). (Note,the RESIO data are also ‘first eye only’.) The distributionof pre-surgery VF-14 scores for the new cohort is furtherright-skewed compared to RESIO, indicating even higherlevels of visual functioning pre-surgery.Post-operative visual functioning, change in outcomesand MCID/MDCFigure 4 reports the post-operative VF-14 scores. Dataare presented for the ‘all first eyes’ and ‘both eyes’ groups. For the ‘all first eye’ group, the mean post-operativeVF-14 score was 92.0 (median: 96.8 interquartilerange: 12.5). For the ‘both eyes’ group, the mean post-operativeVF-14 score was 94.8 (median: 97.9, interquartilerange: 9.0).The vast majority of all patients had a post-operativescore above 85. The ‘all first eye’ and ‘both eyes’ groupsdiffer at the top end of the scale: in excess of 60% of the‘both eyes’ cohort report a score of 95 or higher, com-pared to approximately 50% of the ‘all first eye’ patients.The data highlight that patients in the ‘all first eye’ groupdo not experience the full magnitude of benefit untiltheir second eye is completed, supporting a focus on‘both eyes’ in looking at outcomes in this patient group.The change in visual functioning (from baseline toseven weeks post-surgery) is reported in Figure 5 andTable 2. For the ‘both eyes’ group, the mean change inVF-14 was 7.5 (standard deviation: 11.3). Despite thisaverage indicating a positive VF-14 change, 17.3% ofpatients reported a decline in visual functioning post-surgery, and a further 5.8% experienced no change. Theremainder, and the majority, of the patient cohort(76.9%) experienced an improvement in visual function.Table 1 Baseline characteristics of participants scheduledfor cataract surgery‘All First Eye’(n = 142)‘Both Eyes’ (n = 55)First Eye/Second EyeBaseline Characteristics Mean (SD) orNumber (%)Mean (SD) orNumber (%)Age 72.8 (8.1) 73.0 (7.2)Female 86 (60.6) 36 (65.5)Visual acuity≥0.5 (20/40) 49 (34.5) 28 (50.9)/41 (74.5)0.2-0.4 (20/100-20/50) 80 (56.3) 24 (43.6)/13 (23.6)≥0.1 (20/200) 13 (9.2) 3 (5.5)/1 (1.8)GlareNone 12 (8.6) 3 (5.5)/3 (5.5)Mild 5 (3.6) 3 (5.5)/2 (3.6)Moderate 105 (75.5) 36 (65.5)/45 (81.8)Severe 17 (12.2) 13 (23.6)/5 (9.1)Age Related Macular DegenerationNone 119 (84.4) 42 (76.4)Mild 20 (14.2) 11 (20.0)Moderate 2 (1.4) 2 (3.6)Severe 0 (0) 0 (0)Ocular ComorbiditiesNone 118 (83.7) 42 (77.8)/43 (79.6)Mild 13 (9.2) 7 (13.0)/7 (13.0)Moderate 9 (6.4) 4 (7.4)/2 (3.7)Severe 1 (0.7) 1 (1.9)/2 (3.7)Extent of Impairment in Visual FunctionNone 1 (0.7) 1 (1.8)/0 (0)Mild 16 (11.3) 5 (9.1)/3 (5.5)Moderate 123 (86.6) 47 (85.5)/52 (94.5)Severe 2 (1.4) 2 (3.6)/0 (0)Ability to Function IndependentlyNot threatened/no difficulties 15 (10.6) 4 (7.3)/3 (5.5)Not threatened but more difficult 68 (47.9) 44 (80.0)/47 (85.5)Threatened but not immediately 51 (35.9) 7 (12.7)/5 (9.1)Immediately threatened or unable 8 (5.6) 0 (0)/0 (0)Indications for first/second eyeSignificant cataract 137 (100) 55 (100)/52 (98.1)Driving 17 (12.4) 9 (16.4)/10 (18.9)Needs better view 0 (0) 0 (0)/1 (1.9)Other medical disease 2 (1.5) 1 (1.8)/1 (1.9)Davis et al. BMC Geriatrics 2012, 12:50 Page 4 of 8http://www.biomedcentral.com/1471-2318/12/50When exploring variation in outcomes by baseline visualacuity (Table 2), a trend is evident: larger gains in visualfunctioning were achieved by patients with poorer baselinevisual acuity. This is an unsurprising finding, given thegreater scope for improvement amongst those with poorerfunctioning, but nevertheless important to document.As indicated earlier, the MCID for the VF-14 is 15.57and the MDC is 10.81 [14]. For individuals in the ‘botheyes’ cohort, 23% achieved an improvement in visualfunction that was at or beyond the MCID threshold and35% saw an improvement beyond the MDC.For the ‘corrected’ vision sub-group, improvements invisual function beyond the MDC and MCID thresholdswere 26% and 39% respectively.DiscussionLet us return to our primary study questions.1What level of visual impairment was seen in patientsscheduled for cataract surgery?The level of visual functioning pre-operatively is high,with a mean VF-14 score of 86.7 and a highly skeweddistribution. The RESIO project, conducted over 10 yearsago, highlighted that the pre-operative visual function inCanada was higher than that for other cohorts in theUnited States, Denmark and Spain [20]. Despite this ini-tial evidence that patients in Canada may be going forsurgery earlier than elsewhere, our new data highlightthat the distribution may have shifted even further tothe right, indicating even higher levels of visual func-tioning pre-operatively.2What level of improvement in visual function wasseen following cataract surgery?Figure 2 Pre-operative VF-14 for the Fraser Health ‘All First Eye’ cohort (n = 142).Figure 3 Pre-operative VF-14 for the RESIO cohort (n = 2840) and Fraser Health ‘All First Eye’ cohort (n = 142).Davis et al. BMC Geriatrics 2012, 12:50 Page 5 of 8http://www.biomedcentral.com/1471-2318/12/50The average gain per patient in visual functioning is 7.5points on the VF-14 scale. However, approximately onein five patients receiving cataract surgery recordedpoorer visual functioning after surgery, and a further onein 15 appeared to experience no change. The variation ingains is largely explained by baseline visual acuity: thegreatest improvements were seen in those with the poor-est acuity levels. This is a finding well supported in theliterature [21]. Specifically, one recent study in the UKdemonstrated that if the average gain per patient in visualfunctioning was 5.5 points on the VF-14 scale, 30% ofoperations would be deemed inappropriate [12]. If aver-age gain per patient in visual functioning was 12.2 pointson the VF-14 scale, 49% of operations would be deemedinappropriate. Of note, in this example inappropriatenesswas defined using threshold for different levels of changein visual function. For example, with a threshold of 5.5on the VF-14 scale, many patients got past this lowthreshold and thus few were deemed inappropriate. Incontrast, with a threshold of 12.2, fewer patients got tothis higher level and thus more were deemed inappropri-ate. Further, they detailed that the method of determininga clinically important difference strongly influenced thepercentage of operations deemed inappropriate [12]. Inthe quest for the best clinical outcomes, which in turndrives efficiency, it seems important to examine thecriteria used for assessing appropriateness of cataractsurgery [2-4].3 Do gains in visual function following cataract surgeryreach the MDC and MCID thresholds, and what arethe implications of these thresholds for clinicalpractice in Canada?The concepts of MDC and MCID are important inmaking judgments concerning value. We should expectthat health gains post intervention achieve at least theMDC; if they do not then we are unable to distinguishbetween actual change and measurement error. Ourhope, of course, is that the MCID threshold forFigure 4 Post-operative VF-14 (‘All First Eye’, n = 142; ‘Both Eyes’, n = 52).Figure 5 Mean VF-14 Change (‘All First Eye’, n = 142; ‘Both Eyes’, n = 52).Davis et al. BMC Geriatrics 2012, 12:50 Page 6 of 8http://www.biomedcentral.com/1471-2318/12/50improvement is reached, providing reassurance thatpatients are routinely experiencing clinically importantimprovements as a result of surgery. The disappointingfinding is that the majority of patients did not meet theVF-14 thresholds of 10.81 and 15.57 for MDC andMCID respectively. The most plausible hypothesis forthis finding is that we are not able to observe a MDC orMCID in most patients because of their high pre-operative visual functioning.Providing refractive correction is necessary to mini-mize visual impairment in cataract surgery patients [22].In our sub-group analysis of patients who had experi-enced vision correction post-surgery, the proportion ofpatients reaching the MCID and MDC thresholds wasonly slightly higher than in the overall ‘both eyes’ cohort.Thus, the conclusion that the majority of patients do notreach the thresholds is robust.In considering the appropriate unit of analysis (i.e., eyeor person), we found that the gains in visual functionare greater when the analysis focused on those whoreceived cataract extractions in both eyes rather thanthose who received the first eye only. Often vision is notcorrected with eye glasses until after the second eye iscompleted. Thus, the magnitude of improvement afterthe first cataract surgery will likely be less and so itseems unfair to assess outcomes for partial procedures.Moving forward, we suggest using ‘both eyes’ (i.e., theperson) for analyses of cataract procedures. The VF-14was designed to be completed by the patient consideringtheir visual functioning with both eyes [18,23]. There-fore, using the person as the unit of analysis aligns withthe original intention of the instrument. This recom-mendation will impact future effectiveness and efficiencyestimates for cataract extraction.Limitations of the VF-14The primary limitation of this study may be the sole useof the VF-14. Although the VF-14 was used due to itswidespread use in the literature to provide a basis forcomparison of our study findings, there is notableskepticism relating to the validity of the VF-14. Giventhat safety and predictability of cataract surgery haveimproved over the years, it is possible that the VF-14 isout of date and that other newer instruments are demon-strated as more responsive to cataract surgery [24]. A fewreasons why the VF-14 is one of the least responsiveinstruments may be related to the structure of the ques-tionnaire responses (i.e., not framed to encourage admis-sion of disability) and the instrument noise [25,26].Although the noise of the VF-14 can be improvedthrough Rasch analysis, we did not include that in thisanalysis because it would then render it impossible tomake meaningful conclusions relating to MDC andMCID values. Thus, our conclusions should be inter-preted keeping the limitations of the VF-14 in mind.This study was conducted as an evaluation and so datawere not collected on socio-economic status, other ac-tivities of daily living and non-ophthalmologic co-mor-bidities. The pre-operative visual acuity was collectedearlier, at the time that the patient was first scheduledfor surgery, than was visual function, which was col-lected at the time of surgery. As a result, visual acuitymay decrease between the time of assessment and im-mediately prior to surgery. The MDC and MCID ana-lyses should be interpreted with caution, given that theformulation of these thresholds is dependent on the vis-ual functioning of the population used. Finally, the idealwould be to map longitudinal outcome trajectories to as-sess the potential longer-term benefits associated withearly cataract surgery.ConclusionsSome patients going forward for cataract surgery havevery high levels of visual function. The consequence ofthis, unsurprisingly, is that clinically important improve-ments in visual function are not being seen in allpatients and so the full value from the intervention isnot being gained. This observation speaks to the poten-tial benefits, from a clinical program management per-spective, of routine collection and evaluation ofthresholds and outcomes data for surgical procedures,such as cataract surgery. Further, future research shouldcontinue to focus analyses on the person (i.e., ‘both eyes’)and consider the longer-term trajectory of benefits fromcataract surgery.Competing interestThe authors declare that they have no competing interests.Authors’ contributionsJD, CIHR postdoctoral fellow, and SB, Director of the Centre for ClinicalEpidemiology and Evaluation, provided expertise that informed theevaluation design, undertook the data analysis, supported the interpretationof results, and led on drafting of the manuscript. HMN was responsible forevaluation design and data collection. MW, Epidemiologist, Department ofEvaluation and Research Services, provided statistical expertise that informedthe evaluation design and supported data analysis and interpretation. SC,Table 2 Mean VF-14 change scores in ‘Both Eyes’ byclinical indicators of severityBaseline Characteristics VF-14Mean Change (SD)Total (n = 52) 7.5 (11.3)Female (n = 34) 6.4 (12.6)Male (n = 18) 9.7 (8.3)Visual Acuity≥0.5 (20/40) (n = 27) 4.2 (10.3)0.2-0.4 (20/100-20/50) (n = 24) 11.5 (12.0)≤0.1 (20/200) (n = 1) 8.9 (5.7)Davis et al. BMC Geriatrics 2012, 12:50 Page 7 of 8http://www.biomedcentral.com/1471-2318/12/50Director of the Department of Evaluation and Research Services, providedleadership and guidance during the evaluation planning and data collectionstage, and supported data interpretation and manuscript preparation. Allauthors reviewed and revised the manuscript.AcknowledgementsDisclosure: The authors have no proprietary or commercial interest in anymaterials discussed in this article.Support: Jennifer Davis is funded by a Canadian Institute of Health Researchand Michael Smith Foundation for Health Research postdoctoral fellowship.Author details1Centre for Clinical Epidemiology & Evaluation, Vancouver Coastal HealthResearch Institute, Vancouver, Canada. 2School of Population and PublicHealth, Centre for Clinical Epidemiology and Evaluation VCH ResearchInstitute, The University of British Columbia, Vancouver, Canada. 3Departmentof Evaluation & Research Services, Fraser Health Authority, Surrey, Canada.Received: 2 March 2012 Accepted: 27 August 2012Published: 3 September 2012References1. World Health Organization: Prevention of Blindness and Deafness. GlobalInitiative for the Elimination of Avoidable Blindness. Community EyeHealth 1998, 11(25):1–3.2. 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J Cataract Refract Surg 2009, 35(9):1509–1517.doi:10.1186/1471-2318-12-50Cite this article as: Davis et al.: Focussing both eyes on healthoutcomes: revisiting cataract surgery. BMC Geriatrics 2012 12:50.Submit your next manuscript to BioMed Centraland take full advantage of: • Convenient online submission• Thorough peer review• No space constraints or color figure charges• Immediate publication on acceptance• Inclusion in PubMed, CAS, Scopus and Google Scholar• Research which is freely available for redistributionSubmit your manuscript at www.biomedcentral.com/submitDavis et al. BMC Geriatrics 2012, 12:50 Page 8 of 8http://www.biomedcentral.com/1471-2318/12/50


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