***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: Background / aims : In diabetics , cataract is associated with higher risk of death . In non-diabetics the data are conflicting , but some indicate an association between one type of cataract ( nuclear ) and increased mortality . The aim of this study was to estimate and compare age and sex specific mortality for elderly people with and without cataract in a population based cohort . Methods : A r and om sample drawn from a defined population of elderly people ( age 65 and older ) registered with 17 general practice groups in north London formed the study cohort and were followed up for 4 years . The age and sex specific mortality from various causes was estimated and compared in those with and without cataract . Results : In non-diabetics ( n=1318 ) , cataract ( lens opacity at baseline ) was significantly associated with higher mortality in women . The age st and ardised death rate per 1000 was 39.8 and 24.8 in women with and without cataract , respectively ( age adjusted hazard ratio 1.7 , confidence limits 1.1 to 2.7 , p=0.032 ) . This was not the case in non-diabetic men ( hazard ratio 0.9 , confidence limits 0.6 to 1.5 , p=0.782 ) . The excess mortality in women with cataract was consistent for cardiovascular , respiratory , and other non-cancer causes of death . There was no association between cataract and mortality from cancer . Conclusions : This study has shown , for the first time , that cataract is associated with higher mortality in women but not in men , among the non-diabetic population . This sex effect suggests that women may be exposed to risk factors that increase both the risk of cataract and mortality , and that men may have little or no exposure to these “ sex specific ” factors . Possible risk factors that warrant further investigation may be those associated with some pregnancy and childbearing experience OBJECTIVE To determine the causes of blindness and visual impairment in a population -based sample of older Americans . METHODS A r and om sample of 3821 residents of Salisbury , Md , between the ages of 65 and 84 years was identified from Medicare records . Sixty-six percent ( 2520 persons ) agreed to undergo an eye examination ; 26 % of the participants were African American . The clinical examination included acuity testing with an Early Treatment Diabetic Retinopathy Study chart and st and ardized refraction testing for those with a visual acuity worse than 20/30 , slitlamp and dilated retinal examination by an ophthalmologist , tonometry , lens and fundus photography , and a suprathreshold visual field test . Visual impairment was defined as a best-corrected acuity in the better-seeing eye worse than 20/40 and better than 20/200 , while blindness was acuity in the better-seeing eye of 20/200 or worse . For those with a visual acuity worse than 20/40 in either eye , one or more causes were assigned by an ophthalmologist and a final cause for each eye was confirmed by a panel of 3 subspecialty ophthalmologists ( O.D.S. , H.A.Q. , and S.B.B. ) based on all available evidence . RESULTS Bilateral presenting acuity worse than 20/40 increased from 4 % in the 65- to 74-year age group to 16 % in the 80- to 84-year age group . One third of those with presenting acuity worse than 20/40 improved to 20/40 or better with refraction . Overall , 4.5 % had a best-corrected acuity worse than 20/40 . African Americans were more likely to remain visually impaired than were whites despite refraction ( odds ratio [ 95 % confidence interval ] , 1.7 [ 1.1 - 2.6 ] ) . Whites were most often impaired or blind from age-related macular degeneration ( 1.2 % vs 0.5 % ; P=.09 ) . African Americans had higher rates of impairment and blindness from cataract or posterior capsular opacification ( 2.7 % vs 1.1 % ; P=.006 ) , glaucoma ( 0.9 % vs 0.1 % ; P=.006 ) , and diabetic retinopathy ( 1.2 % vs 0.2 % ; P=. 004 ) . CONCLUSIONS More than half of those with visual impairment or blindness had conditions that were either surgically treatable or potentially preventable . African Americans had a disproportionate number of blinding diseases , particularly those amenable to eye care intervention . Targeted interventions for specific population s to increase appropriate eye care use would greatly improve vision and function in older Americans . Arch Ophthalmol . 2000;118:819 - Abstract Objective : To estimate the magnitude of serious eye disorders and of visual impairment in a defined elderly population of a typical metropolitan area in Engl and , and to assess the frequency they were in touch with , or known to , the eye care services . Design : Cross sectional survey using two stage cluster r and om sampling . Setting : General practice s in north London . Subjects : R and om sample of people aged 65 and older , drawn from a defined population of elderly people registered with 17 general practice groups . Main outcome measures : Proportions and population prevalence estimates were determined for visual acuity , assessed with the person 's own spectacles ( if any ) , classified into four categories : prevalence of cataract , age related macular degeneration , and refractive error causing visual impairment and of definite primary open angle glaucoma ; and status of contact with eye services . Results : 1547 of 1840 ( 84 % ) eligible people were examined . The population prevalence of bilateral visual impairment ( visual acuity < 6/12 ) was 30 % , of which 72 % was potentially remediable . 92 of these 448 cases ( 21 % ) had visual acuity < 6/60 ( “ blindness ” ) in one or both eyes . Prevalence of cataract causing visual impairment was 30 % ; 88 % of these people were not in touch with the eye services . The prevalence of vision impairing , age related macular degeneration was 8 % and of glaucoma ( definite cases ) was 3 % . Three quarters of the people with definite glaucoma were not known to the eye services . Conclusions : Untreated visual impairment and eye disorders affect a substantial proportion of people aged 65 years and older . These findings should contribute to the setting up of future strategies for preservation of sight and eye health services in general . Key messages Data have not been adequate to reliably estimate the extent of visual impairment and serious eye disease in metropolitan areas in Britain Data from north London shows that 30 % of a sample of the population aged 65 or older are visually impaired in both eyes More than 72 % of the bilateral visual impairment was potentially remediable by surgery or glasses , nearly one in three people had visually impairing cataract , and 88 % of these people were not in touch with eye services Eye problems were more prevalent in people living in relatively underprivileged OBJECTIVES To describe the age-specific prevalence of common eye diseases causing bilateral visual impairment  and estimate the total number of Australians with cause-specific visual impairment . METHODS Cluster-stratified r and om sample of 5147 residents aged 40 years and older from urban and rural areas and aged-care facilities . Participants completed a st and ardized interview and eye examination . Four levels of bilateral visual impairment were defined : less than 20/40 to 20/60 and /or homonymous hemianopia ( mild ) , less than 20/60 to 20/200 or better and /or less than 20 degrees to 10 degrees radius field ( moderate ) , less than 20/200 to 10/200 and /or less than 10 degrees to 5 degrees radius field ( severe ) , and less than 1O/ 200 and /or less than 50 radius field ( profound ) . The major cause of vision loss was identified for all participants found to be visually impaired . RESULTS Uncorrected refractive error was the most common cause of bilateral visual impairment across all decades of life , rising from 0.5 % in 40- to 49-year-olds to 13 % among those aged 80 years and older . Prevalence of visual impairment due to diabetic retinopathy was 0.7 % in 50- to 59-year-olds and 0.8 % in those older than 80 years . Visual impairment due to glaucoma had a prevalence of 0.7 % among 60-year-olds and rose to 4 % of those older than 90 years . The prevalence of visual impairment due to cataract ( only present in those aged 70 years or older ) rose from 0.6 % to 11 % in those older than 90 years , and the prevalence of visual impairment due to age-related macular degeneration rose from 0.8 % to 16 % in those older than 90 years . CONCLUSIONS The predominant causes of visual impairment change with age . Recognition of these patterns is fundamental for early diagnosis and treatment of eye disease and , where appropriate , referral for rehabilitation PURPOSE To study the cause-specific prevalence of eye diseases causing  bilateral visual impairment in Australian adults . DESIGN Two-site , population -based cross-sectional study . PARTICIPANTS Participants were aged 40 years and older and resident in their homes at the time of recruitment for the study . The study was conducted during 1992 through 1996 . METHODS The study uses a cluster stratified r and om sample of 4744 participants from two cohorts , urban , and rural Victoria . Participants completed a st and ardized interview and eye examination , including presenting and best-corrected visual acuity , visual fields , and dilated ocular examination . The major cause of vision loss was identified for all participants found to be visually impaired . Population -based prevalence estimates are weighted to reflect the age and gender distribution of the two cohorts in Victoria . MAIN OUTCOME MEASURES Visual impairment was defined by four levels of severity on the basis of best-corrected visual acuity or visual field : < 6/18 > or = 6/60 and /or < 20 degrees > or = 10 degrees radius field , moderate vision impairment ; severe vision impairment , < 6/60 > or = 3/60 and /or < 10 degrees > or = 5 degrees radius field ; and profound vision impairment < 3/60 and /or < 5 degrees radius field . In addition , less-than-legal driving vision , < 6/12 > or = 6/18 , and /or homonymous hemianopia were defined as mild vision impairment . In Australia , legal blindness includes severe and profound vision impairment . RESULTS The population -weighted prevalence of diseases causing less-than-legal driving or worse impairment in the better eye was 42.48/1000 ( 95 % confidence interval [ CI ] , 30.11 , 54.86 ) . Uncorrected refractive error was the most frequent cause of bilateral vision impairment , 24.68/1000 ( 95 % CI , 16.12 , 33.25 ) , followed by age-related macular degeneration ( AMD ) , 3.86/1000 ( 95 % CI , 2.17 , 5.55 ) ; other retinal diseases , 2.91/1000 ( 95 % CI , 0.74 , 5.08 ) ; other disorders , 2.80/1000 ( 95 % CI , 1.17 , 4.43 ) ; cataract , 2.57/1000 ( 95 % CI , 1.38 , 3.76 ) ; glaucoma , 2.32/1000 ( 95 % CI , 0.72 , 3.92 ) ; neuro-ophthalmic disorders , 1.80/1000 ( 95 % CI , 0 , 4.11 ) ; and diabetic retinopathy , 1.53/1000 ( 95 % CI , 0.71 , 2.36 ) . The prevalence of legal blindness was 5.30/1000 ( 95 % CI , 3.24 , 7.36 ) . Although not significantly different , the causes of legal blindness were uncorrected refractive errors , AMD , glaucoma , other retinal conditions , and other diseases . CONCLUSIONS Significant reduction of visual impairment may be attained with the application of current knowledge in refractive errors , diabetes mellitus , cataract , and glaucoma . Although easily preventable , uncorrected refractive error remains a major cause of vision impairment OBJECTIVE To describe the causes of blindness and visual impairment in a population -based sample of Hispanics . DESIGN A cross-sectional study . PARTICIPANTS A r and om sample of 4774 Hispanic residents of Santa Cruz and Pima Counties in Southern Arizona aged 40 years and older who participated in Proyecto VER ( Vision Evaluation and Research ) . TESTING Subjects were interviewed and underwent a thorough ophthalmic examination . Presenting and best-corrected visual acuity was determined using the Early Treatment of Diabetic Retinopathy Study protocol , followed by a st and ardized ophthalmic examination to determine the causes of visual loss . Anterior and posterior segment specialists in ophthalmology confirmed the causes . MAIN OUTCO 
    Output:
    
Overall the prevalence was higher in the older population , especially among women .
The increasing prevalence associated with age predicts an increasing burden of cataract to health services , this being particularly related to the ageing of the population