title: [Prevalence and causes of blindness and moderate and severe visual impairment among adults aged 50 years or above in Changji City of Xinjiang Uygur Autonomous Region: the China Nine-Province survey].
abstract: OBJECTIVE
  To investigate the prevalence and causes of blindness and moderate and severe visual impairment among adults aged ≥ 50 years in Changji City of Xinjiang Uygur Autonomous Region, China.
  
  
  METHODS
  It was a population-based cross-section study.Geographically defined cluster sampling was used in randomly selecting 5714 individuals aged ≥ 50 years in Changji City. The survey was preceded by a pilot study where operational methods were refined and quality assurance evaluation was carried out. All participants were enumerated through village registers followed door-to-door visits.Eligible individuals were invited to received visual acuity measurement and eye examination. Prevalence of blindness and moderate and severe visual impairment was calculated according to different age, gender or education. And the reasons of blindness were analyzed.Statistical analyses were performed using Stata/SE Statistical Software, release 9.0. Chi-square test was used to investigate the association of age, gender and education with presenting and best corrected visual acuity.
  
  
  RESULTS
  Five thousands seven hundreds and fourteen individuals were enumerated and 5250 persons were examined, the response rate was 91.88%. Based on the criteria of World Health Organization visual impairment classification in 1973, the prevalence of blindness and moderate and severe visual impairment defined as best corrected visual acuity was 0.74% (39/5250) and 3.83% (201/5250) respectively. The prevalence of blindness and moderate and severe visual impairment defined as presenting visual acuity was 1.33% (70/5250) and 8.02% (421/5250) respectively. The prevalence of blindness and moderate and severe visual impairment was higher in aged (trend χ(2) = 617.06, P = 0.000) , illiterate (trend χ(2) = 222.35, P = 0.000) persons. Cataract and was the first leading cause of blindness and visual impairment, the retinal diseases, including age-related macular degeneration, high myopic retinopathy, and diabetic retinopathy, were the second cause of blindness and visual impairment.Un-corrected refractive error was also the important cause of the visual blindness.
  
  
  CONCLUSIONS
  The prevalence of blindness and moderate and severe visual impairment is not high among older adults aged ≥ 50 years in Changji City. The first main causes of blindness and visual impairment includes cataract, retinal diseases and un-corrected refractive error.
authors: Department of Ophthalmology, Changji Chinese Traditional Medicine Hospital, Changji 831100, China.
authors: Xian-zhi
authors: XZ
authors: Ma
authors: Email: zhjialiang@163.com.
authors: Jia-liang
authors: JL
authors: Zhao
authors: Leon B
authors: LB
authors: Ellwein
authors: Bin
authors: B
authors: Wei
authors: Jing
authors: J
authors: Chen
authors: Ying
authors: Y
authors: Ye
authors: Xiao-dong
authors: XD
authors: Tang
authors: Mei
authors: M
authors: Yang
authors: Yu
authors: Y
authors: Wang
authors: Xue-cheng
authors: XC
authors: Gao
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001766:Blindness / Q000453:epidemiology*; D002386:Cataract / Q000453:epidemiology; D002681:China / Q000453:epidemiology; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012164:Retinal Diseases / Q000453:epidemiology*