title: Prevalence and causes of low vision and blindness in an urban population: The Chennai Glaucoma Study.
abstract: OBJECTIVE
  To evaluate the prevalence and causes of low vision and blindness in an urban south Indian population.
  
  
  METHODS
  Population-based cross-sectional study. Exactly 3850 subjects aged 40 years and above from Chennai city were examined at a dedicated facility in the base hospital.
  
  
  METHODS
  All subjects had a complete ophthalmic examination that included best-corrected visual acuity. Low vision and blindness were defined using World Health Organization (WHO) criteria. The influence of age, gender, literacy, and occupation was assessed using multiple logistic regression.
  
  
  METHODS
  Chi-square test, t-test, and multivariate analysis were used.
  
  
  RESULTS
  Of the 4800 enumerated subjects, 3850 subjects (1710 males, 2140 females) were examined (response rate, 80.2%). The prevalence of blindness was 0.85% (95% CI 0.6-1.1%) and was positively associated with age and illiteracy. Cataract was the leading cause (57.6%) and glaucoma was the second cause (16.7%) for blindness. The prevalence of low vision was 2.9% (95% CI 2.4-3.4%) and visual impairment (blindness + low vision) was 3.8% (95% CI 3.2-4.4%). The primary causes for low vision were refractive errors (68%) and cataract (22%).
  
  
  CONCLUSIONS
  In this urban population based study, cataract was the leading cause for blindness and refractive error was the main reason for low vision.
authors.affiliation: Department of Glaucoma Project, Chennai Glaucoma Study, Vision Research Foundation, Sankara Nethralaya, Chennai, Tamil Nadu, India.
authors.forename: Lingam
authors.initials: L
authors.lastname: Vijaya
authors.forename: Ronnie
authors.initials: R
authors.lastname: George
authors.forename: Rashima
authors.initials: R
authors.lastname: Asokan
authors.forename: Lokapavani
authors.initials: L
authors.lastname: Velumuri
authors.forename: Sathyamangalam Ve
authors.initials: SV
authors.lastname: Ramesh
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001766:Blindness / Q000453:epidemiology* / Q000209:etiology; D002386:Cataract / Q000150:complications*; D003430:Cross-Sectional Studies; D005260:Female; D005901:Glaucoma / Q000150:complications*; D006801:Humans; D007194:India / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012030:Refractive Errors / Q000150:complications*; D012189:Retrospective Studies; D014505:Urban Population; D015354:Vision, Low / Q000453:epidemiology* / Q000209:etiology; D014792:Visual Acuity