***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: OBJECTIVE first eye cataract surgery reduces the risk of falling . Most cataracts in elderly people are bilateral . Some binocular functions ( e.g. stereopsis ) are associated with falls . We aim ed to determine if second eye cataract surgery reduces the risk of falling and to measure associated health gain . STUDY DESIGN AND SETTING we r and omised 239 women over 70 , who had been referred to a hospital ophthalmology department , with one unoperated cataract , to expedited ( approximately 4 weeks ) or routine ( 12 months wait ) surgery .  Falls were ascertained by diary , with follow-up every 3 months for 12 months . We measured health status after 6 months . RESULTS visual function ( especially stereopsis ) improved in the operated group . Over 12 months follow-up , 48 ( 40 % ) operated participants fell at least once , 22 ( 18 % ) fell more than once . Forty-one ( 34 % ) unoperated participants fell at least once , 22 ( 18 % ) fell more than once . Rate of falling was reduced by 32 % in the operated group , but this was not statistically significant ( rate ratio 0.68 , 95 % CI 0.39 , 1.19 , P = 0.18 ) . Confidence , visual disability and h and icap all improved in the operated compared with the control group . CONCLUSION second eye cataract surgery improves visual disability and general health status . The effect on rate of falling remains uncertain PURPOSE To investigate the responsiveness of 16 question naires used in cataract surgery outcomes . DESIGN Prospect i ve , observational study . PARTICIPANTS Patients at the Ophthalmology Eye Clinic , Flinders Medical Centre , Adelaide , Australia , and 1 matched eye clinic in Sweden . METHODS Sixteen Rasch-scaled cataract surgery question naires  were completed before and 6 months after surgery . These were : the Cataract Symptom Scale , 6 versions of the National Eye Institute Visual Function Question naire , the Quality of Life and Vision Function Question naire , the Cataract TyPE Specification , the Visual Activities Question naire , the Visual Disability Assessment ( VDA ) , the Visual Function and Quality of Life question naire , the Visual Function Index , Catquest-9SF , the Visual Symptoms and Quality of Life question naire , and the Cataract Outcomes Question naire .  Responsiveness was calculated with the effect size ( ES ) statistic ( change in question naire score divided by pooled st and ard deviation of the preoperative and postoperative scores ) . MAIN OUTCOME MEASURES Question naire responsiveness to cataract surgery ( ability to detect clinical ly important change ) . RESULTS All 16 question naires and their subscales were responsive to cataract surgery , with visual functioning scales being more responsive than socioemotional scales and some subscales being less responsive . The largest ES was for the Catquest-9SF ( 1.45 ; 95 % confidence interval [ CI ] , 1.22 - 1.67 ) , which was the only instrument with a mean and 95 % CI of more than 1.0 ( very large ES ) . Three measures had very large ESs and 95 % CIs of more than 0.80 ( large ES ) : the VDA ( activity limitations and subscale ) and the Cataract Outcomes Question naire , although their 95 % CIs overlapped with a number of other instruments . CONCLUSIONS The Catquest-9SF is short and highly responsive to cataract surgery , and so is ideal for measuring visual functioning outcomes . Other instruments may be preferred to measure different constructs . FINANCIAL DISCLOSURE(S ) The author(s ) have no proprietary or commercial interest in any material s discussed in this article Purpose To examine the distribution in the population of indications for cataract extraction  in order to relate dem and for this procedure to the capacity for satisfying it . Methods An age-stratified r and om population sample of 2783 individuals aged 55 years and over was taken from inner-city , urban and rural areas of Avon and Somerset . The requirement for cataract extraction was estimated on the basis of measures of vision-related quality of life , refracted visual acuity , and application of the Oxford Clinical Cataract Classification and Grading System . Data were also collected concerning suitability for surgery , including relative contraindications to surgery and whether participants considered their eyesight bad enough to merit surgery . Three sets of composite indications were defined . Results Estimated prevalent requirements for cataract extraction  for the three sets of composite criteria were : 29 per 1000 aged over 55 years ( 95 % CI 20 - 41 ) for the most inclusive criterion ; 17 per thous and ( 95 % CI 10 - 27 ) for the intermediate criterion ; and 7 per thous and ( 95 % CI 3 - 14 ) for the most stringent criterion . These rates are equivalent to a national prevalent requirement for Engl and of 384 000 for the most inclusive criterion . If the approximately 15 % of individuals whose desire or fitness for surgery was question able are removed from this estimate , the prevalent requirement , including the backlog from previous unsatisfied dem and , becomes 325 000 individuals . Conclusions The findings suggest only a modest imbalance between supply and dem and for cataract surgery . In particular there was a very small prevalence of untreated severe cataract , less than the annual health service surgical capacity , suggesting that the current National Health Service surgical capacity is adequate for cases of severe cataract Background If decisions on health care spending are to be as rational and objective as possible , knowledge on cost-effectiveness of routine care is essential . Our aim , therefore , was to evaluate the cost-utility of routine cataract surgery in a real-world setting . Methods Prospect i ve assessment of health-related quality of life ( HRQoL ) of patients undergoing cataract surgery . 219 patients ( mean ( SD ) age 71 ( 11 ) years ) entering cataract surgery ( in 87 only first eye operated , in 73 both eyes operated , in 59 first eye had been operated earlier ) filled in the 15D HRQoL question naire before and six months after operation . Direct hospital costs were obtained from a clinical patient administration data base and cost-utility analysis performed from the perspective of the secondary care provider extrapolating benefits of surgery to the remaining statistical life-expectancy of the patients . Results Mean ( SD ) utility score ( on a 0–1 scale ) increased statistically insignificantly from 0.82 ( 0.13 ) to 0.83 ( 0.14 ) . Of the 15 dimensions of the HRQoL instrument , only seeing improved significantly after operation . Mean utility score improved statistically significantly only in patients reporting significant or major preoperative seeing problems . Of the subgroups , only those whose both eyes were operated during follow-up showed a statistically significant ( p < 0.001 ) improvement . Cost per quality -adjusted life year ( QALY ) gained was € 5128 for patients whose both eyes were operated and € 8212 for patients with only one eye operated during the 6-month follow-up . In patients whose first eye had been operated earlier mean HRQoL deteriorated after surgery precluding the establishment of the cost per QALY . Conclusion Mean utility gain after routine cataract surgery in a real-world setting was relatively small and confined mostly to patients whose both eyes were operated . The cost of cataract surgery per quality -adjusted life year gained was much higher than previously reported and associated with considerable uncertainty OBJECTIVE To perform a reference case cost-utility analysis of  second-eye cataract surgery  by using the current literature on cataract outcomes and complications . DESIGN Computer-based econometric modeling . METHODS Visual acuity data of patients treated and observed over a 4-month postoperative period were obtained from the U.S. National Cataract Patient Outcomes Research Team report . The results from this prospect i ve study were combined with those of other studies that investigated the complication rates of cataract surgery to complete the cohort of patients and outcomes . These synthesized data were incorporated with time trade-off utility values , which accounted for prior successful cataract surgery in the fellow eye . Cost-utility determinations were made with decision analysis , and present value modeling was used to account for the time value of money and health state consequences . MAIN OUTCOME MEASURES The number of quality -adjusted life-years ( QALYs ) gained was calculated for the study group undergoing second-eye cataract surgery  , assuming that the postoperative vision in the second eye was equivalent to the vision in the first eye after surgery ( 20/27 ) . This was divided into the cost of the procedure to find the number of year 2001 nominal U.S. dollars spent per QALY gained . RESULTS Second-eye cataract surgery , as compared with unilateral pseudophakia , result ed in a mean gain of 1.31 undiscounted QALYs per patient treated . A 3 % annual discount rate , dependent on the duration of benefit , was used , yielding 0.92 discounted QALYs gained over a 12-year life expectancy . The mean discounted cost of treatment for each patient totaled 2509 US dollars . The cost divided by the QALYs gained ( benefit ) result ed in 2727 US dollars per QALY gained for this procedure . Sensitivity analysis varying costs and utility values revealed a range from 2045 US dollars to 3649 US dollars per QALY gained . CONCLUSIONS Second-eye cataract surgery is an extremely cost-effective procedure when compared with other interventions across medical specialties . The cost-effectiveness of second-eye surgery diminishes only slightly from the 2023 US dollars per QALY gained from first-eye cataract surgery . This suggests that patients with good vision in one eye and visual loss from cataract in the fellow eye derive substantial benefit from cataract extraction Purpose To determine the basis for the dramatic decline in coarse stereopsis that occurs with age . Methods The Frisby test was used to assess stereopsis in a large sample of r and omly selected persons over the age of 58 years . A number of other vision functions were also assessed in the same persons . The data were used to address the question of whether the decline in stereopsis reflects age-related alterations in cortical stereopsis mechanisms themselves ( e.g. , disparity detectors ) or a degradation of the signal reaching the cortex as a result of alterations in earlier visual components . Two of three vision measures were binocular and thus reflect predominantly the function of the better eye . Results We find , as many others have reported , that even very coarse stereopsis declines dramatically with age . Despite not having separately assessed each eye , we find that among those selected to have good ocular function there was no significant decline in coarse stereopsis with age . Conclusion These findings suggest that the enormous decline in coarse stereopsis with age can be accounted for by alterations in early stages of vision processing OBJECTIVE To compare visual outcomes obtained following  cataract surgery in 4 sites in North America and Europe where considerable differences in the organization of care and patterns of clinical practice have been previously described . METHODS Patients scheduled for first eye-cataract surgery and aged 50 years or older were enrolled consecutively in a prospect i ve multicenter study that collected clinical and patient interview data preoperatively and postoperatively . From the United States , 772 patients were enrolled ; from the Province of Manitoba ( Canada ) , 159 ; from Denmark , 291 ; and from the City of Barcelona ( Spain ) , 200 . Preoperative and 4-month postoperative visual acuity was obtained for 92 % of the patients ( n = 1291 ) . RESULTS The mean 4-month postoperative visual acuity of eyes operated on varied significantly across the 4 sites ( P < .001 ) and had the following Snellen decimal fraction measurements : 0.49 in Barcelona , 0.65 in Denmark , 0.66 in Manitoba , and 0.74 in the United States . However , while crude visual acuity outcome figures varied significantly , no significant difference was observed across the 4 sites regarding the risk of poorer visual outcome after controlling for differences in age , preoperative visual acuity , and general health status for patients with no ocular comorbidity . Older age , poorer preoperative visual acuity , poorer preoperative general health status , and coexisting ocular comorbidity were predictors of a poorer visual outcome . CONCLUSION A previously identified variation in treatment modalities across the 4 sites did not seem to affect patients ' visual acuity outcomes Background The appropriateness of cataract surgery procedures has been question ed , the suggestion being that the surgery is sometimes undertaken too early in the disease progression . Our three study questions were : What is the level of visual impairment in patients scheduled for cataract surgery  ? What is the improvement following surgery ? Given the thresholds for a minimal detectable change ( MDC ) and a minimal clinical ly important difference ( MCID ) , do gains in visual function reach the MDC and MCID thresholds ? Methods The sample included a prospect i ve cohort of cataract surgery patients from four Fraser Health Authority ophthalmologists .  Visual function ( VF-14 ) was assessed pre-operatively and at seven weeks post-operatively . Two groups 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 and proportion 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 full visual function ) . The mean change in VF-14 for the ' both eyes ' group was 7.5 . Twenty 
    Output:
    
The RCTs assessed visual acuity , contrast sensitivity , stereopsis and several measures of HRQoL. Improvements in binocular visual acuity and contrast sensitivity were small and unlikely to be of clinical significance , but stereopsis was improved to a clinical ly meaningful extent following second-eye surgery .
Model results were most sensitive to changes in the utility gain associated with second-eye surgery , but otherwise robust to changes in parameter values .
Second-eye cataract surgery is generally cost-effective based on the best available data and under most assumptions .