title: Prevalence and causes of low vision and blindness in a rural chinese adult population: the Handan Eye Study.
abstract: OBJECTIVE
  To describe the prevalence and causes of low vision and blindness in a rural population in Northern China.
  
  
  METHODS
  Population-based, cross-sectional study.
  
  
  METHODS
  A study of 6830 Han Chinese aged 30 years and older was conducted between October 2006 and October 2007 in rural Yongnian County in Handan, Northern China.
  
  
  METHODS
  Clustered samples of adults aged 30 years or more residing in 13 residential villages were selected randomly and were invited to participate the Handan Eye Study. Participants underwent a comprehensive eye examination, including standardized visual acuity (VA) tests using logarithm of the minimum angle resolution charts. Prevalence was age- and gender-standardized to the 2000 China Census.
  
  
  METHODS
  Low vision was defined as VA <20/60 but >/=20/400, and blindness was defined as VA <20/400 following the Modified World Health Organization (WHO) definitions. Primary causes of low vision and blindness were determined by study ophthalmologists according to WHO definitions.
  
  
  RESULTS
  Six thousand eight hundred thirty (90.4%) of 7577 eligible individuals participated in the study, and 6799 (89.7%) had VA data available. Population-weighted prevalence of presenting bilateral blindness was 0.6% and bilateral low vision was 4.7% for persons 30 years of age and older. Based on best-corrected visual acuity (BCVA), the corresponding prevalence of blindness was 0.5% and that of low vision was 1.0%. Blindness and low vision were strongly age related (P<0.05). Cataract was the predominant cause of presenting bilateral blindness (36.6%), whereas undercorrected refractive error was the predominant cause of presenting low vision (78.4%). After refractive correction, cataract became the first leading cause of blindness (41.9%), and low vision (48.2%), myopic retinopathy (16.1%), glaucoma (9.7%), and corneal opacity (9.7%) were other common causes of blindness defined using BCVA.
  
  
  CONCLUSIONS
  A higher prevalence of blindness and low vision was seen in this rural Chinese sample than has been reported from urban Chinese populations. The estimated numbers with BCVA-defined low vision and blindness in 2020, based on best-corrected vision in rural Chinese adults aged 30 years or more, is expected to be 12.4 million and 2.9 million, respectively. Predominant causes of low vision and blindness in China are treatable.
authors.affiliation: Beijing Tongren Eye Center, Capital University of Medical Sciences, Beijing, China.
authors.forename: Yuan Bo
authors.initials: YB
authors.lastname: Liang
authors.forename: David S
authors.initials: DS
authors.lastname: Friedman
authors.forename: Tien Yin
authors.initials: TY
authors.lastname: Wong
authors.forename: Si Yan
authors.initials: SY
authors.lastname: Zhan
authors.forename: Lan Ping
authors.initials: LP
authors.lastname: Sun
authors.forename: Jie Jin
authors.initials: JJ
authors.lastname: Wang
authors.forename: Xin Rong
authors.initials: XR
authors.lastname: Duan
authors.forename: Xiao Hui
authors.initials: XH
authors.lastname: Yang
authors.forename: Feng Hua
authors.initials: FH
authors.lastname: Wang
authors.forename: Qiang
authors.initials: Q
authors.lastname: Zhou
authors.forename: Ning Li
authors.initials: NL
authors.lastname: Wang
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D044466:Asian People / Q000208:ethnology*; D001766:Blindness / Q000208:ethnology* / Q000209:etiology; D002681:China / Q000453:epidemiology; D003430:Cross-Sectional Studies; D005128:Eye Diseases / Q000150:complications; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012424:Rural Population / Q000706:statistics & numerical data*; D014787:Vision Tests; D015354:Vision, Low / Q000208:ethnology* / Q000209:etiology; D014792:Visual Acuity; D019987:Persons with Visual Disabilities / Q000706:statistics & numerical data*; D014944:World Health Organization