title: Prevalence and causes of blindness and visual impairment and their associated risk factors, in three tribal areas of Andhra Pradesh, India.
abstract: OBJECTIVE
  To assess the prevalence of blindness and visual impairment (VI), their associated causes and underlying risk factors in three tribal areas of Andhra Pradesh, India and compare this data in conjunction with data from other countries with low and middle income settings.
  
  
  METHODS
  Using a validated Rapid Assessment of Avoidable Blindness methodology, a two stage sampling survey was performed in these areas involving probability proportionate to size sampling and compact segment sampling methods. Blindness, VI and severe visual impairment (SVI) were defined as per the WHO guidelines and Indian definitions.
  
  
  RESULTS
  Based on a prior enumeration, 7281 (97.1%) subjects were enrolled (mean age = 61.0+/-7.9 years). Based on the presenting visual acuity (PVA), the prevalences of VI, SVI and blindness were 16.9% (95% CI: 15.7-18.1), 2.9% (95% CI: 2.5-3.4), and 2.3% (95% CI: 1.9-2.7), respectively. When based on the Pinhole corrected visual acuity (PCVA), the prevalences were lower in VI (6.2%, 95% CI: 5.4-6.9), SVI (1.5%, 95% CI: 1.2-1.9) and blindness (2.1%, 95% CI: 1.7-2.5). Refractive error was the major cause of VI (71.4%), whereas, cataract was the major cause of SVI and blindness (70.3%). Based on the PVA, the odds ratio (OR) of blindness increased in the age groups of 60-69 years (OR = 3.8, 95% CI: 2.8, 5.1), 70-79 years (OR = 10.6, 95% CI: 7.2, 15.5) and 80 years and above (OR = 30.7, 95% CI: 19.2, 49). The ORs were relatively higher in females (OR = 1.3, 95% CI: 1.0, 1.6) and illiterate subjects (OR = 4.3, 95% CI: 2.2, 8.5), but lower in those wearing glasses (OR = 0.2, 95% CI: 0.1, 0.4).
  
  
  CONCLUSIONS
  This is perhaps the first study to assess the prevalence of blindness and VI in these tribal regions and the majority of the causes of blindness and SVI were avoidable (88.5%). These findings may be useful for planning eye care services in these underserved regions.
authors.affiliation: Biostatistics, Harvard School of Public Health, Boston, Massachusetts, United States of America.
authors.forename: Nakul
authors.initials: N
authors.lastname: Singh
authors.affiliation: Andhra Pradesh Right to Sight Society, Hyderabad, India; School of Optometry and Vision Science, University of New South Wales, Sydney, Australia.
authors.forename: Shiva Shankar
authors.initials: SS
authors.lastname: Eeda
authors.affiliation: Andhra Pradesh Right to Sight Society, Hyderabad, India; School of Optometry and Vision Science, University of New South Wales, Sydney, Australia.
authors.forename: Bala Krishna
authors.initials: BK
authors.lastname: Gudapati
authors.affiliation: Andhra Pradesh Right to Sight Society, Hyderabad, India; School of Optometry and Vision Science, University of New South Wales, Sydney, Australia.
authors.forename: Srinivasa
authors.initials: S
authors.lastname: Reddy
authors.affiliation: Internal Medicine, St. Vincent Charity Medical Center, Cleveland, Ohio, United States of America.
authors.forename: Pushkar
authors.initials: P
authors.lastname: Kanade
authors.affiliation: Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, United States of America; Department of Internal Medicine, Wright Center for Graduate Medical Education, Pennsylvania, United States of America.
authors.forename: Ghanshyam Palamaner Subash
authors.initials: GP
authors.lastname: Shantha
authors.affiliation: Brien Holden Eye Research Centre, L.V. Prasad Eye Institute, Banjara Hills, Hyderabad, India; Allen Foster Research Centre for Community Eye Health, GPR International Centre for Advancement of Rural Eye care, L V Prasad Eye Institute, Hyderabad, India.
authors.forename: Padmaja Kumari
authors.initials: PK
authors.lastname: Rani
authors.affiliation: Brien Holden Eye Research Centre, L.V. Prasad Eye Institute, Banjara Hills, Hyderabad, India.
authors.forename: Subhabrata
authors.initials: S
authors.lastname: Chakrabarti
authors.affiliation: Brien Holden Eye Research Centre, L.V. Prasad Eye Institute, Banjara Hills, Hyderabad, India; Allen Foster Research Centre for Community Eye Health, GPR International Centre for Advancement of Rural Eye care, L V Prasad Eye Institute, Hyderabad, India.
authors.forename: Rohit C
authors.initials: RC
authors.lastname: Khanna
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001766:Blindness / Q000453:epidemiology* / Q000209:etiology; D002386:Cataract / Q000453:epidemiology*; D005260:Female; D006801:Humans; D007194:India / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012030:Refractive Errors / Q000453:epidemiology* / Q000209:etiology / Q000628:therapy; D012307:Risk Factors; D014786:Vision Disorders / Q000453:epidemiology / Q000209:etiology / Q000628:therapy