title: The impact of cataract, cataract types, and cataract grades on vision-specific functioning using Rasch analysis.
abstract: OBJECTIVE
  To determine the impact of cataracts and their types and grades on vision-specific functioning.
  
  
  METHODS
  Prospective population-based cross-sectional study.
  
  
  METHODS
  The Singapore Indian Eye Study examined 3400 of 4497 (75.6% response rate) ethnic Indians 40 years of age and older living in Singapore. Three thousand one hundred sixty-eight (93.2%) fulfilled inclusion criteria with complete information for final analysis. Cataracts were assessed on slit-lamp examination and were graded according to the Lens Opacity Classification System III. Vision-specific functioning scores were explored with the Visual Function scale, validated using Rasch analysis.
  
  
  RESULTS
  Two hundred sixty-nine (8.5%) and 740 (23.4%) of the study participants had unilateral and bilateral cataracts, respectively, and 329 (10.4%), 800 (25.2%), and 128 (4.1%) participants had nuclear, cortical, and posterior subcapsular (PSC) cataracts, respectively. In multivariate linear regression models, the presence of bilateral rather than unilateral cataract (β = -0.12; 95% confidence interval, -0.20 to 0.00) was associated independently with poorer vision-specific functioning, even after adjusting for undercorrected refractive error (β = -0.11; 95% confidence interval, -0.21 to 0.00). Bilateral nuclear, cortical, and PSC cataracts also were associated with poorer vision-specific functioning (β = -0.31, -0.15, and -1.15, respectively), with combinations of them having even greater impact. Significantly poorer vision-specific functioning occurred at Lens Opacity Classification System grades 4 (nuclear opalescence), 5 (nuclear color), 3 (cortical), and 1 (PSC) or higher.
  
  
  CONCLUSIONS
  People with bilateral but not unilateral cataracts experience difficulty with performing vision-specific daily activities independent of refractive error, with PSC cataracts and cataract combinations having the greatest impact. Cataract types cause poorer vision-specific functioning beginning at different severity grades.
authors.affiliation: Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Republic of Singapore.
authors.forename: Merwyn
authors.initials: M
authors.lastname: Chew
authors.forename: Peggy Pei-Chia
authors.initials: PP
authors.lastname: Chiang
authors.forename: Yingfeng
authors.initials: Y
authors.lastname: Zheng
authors.forename: Raghavan
authors.initials: R
authors.lastname: Lavanya
authors.forename: Renyi
authors.initials: R
authors.lastname: Wu
authors.forename: Seang Mei
authors.initials: SM
authors.lastname: Saw
authors.forename: Tien Yin
authors.initials: TY
authors.lastname: Wong
authors.forename: Ecosse L
authors.initials: EL
authors.lastname: Lamoureux
mesh_terms: D000203:Activities of Daily Living; D000328:Adult; D000368:Aged; D002386:Cataract / Q000145:classification* / Q000503:physiopathology*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007194:India / Q000208:ethnology; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011594:Psychometrics; D011788:Quality of Life; D015203:Reproducibility of Results; D018434:Sickness Impact Profile; D012846:Singapore / Q000453:epidemiology; D011795:Surveys and Questionnaires; D014786:Vision Disorders / Q000503:physiopathology*; D014792:Visual Acuity / Q000502:physiology*