title: Causes of blindness and visual impairment in urban and rural areas in Beijing: the Beijing Eye Study.
abstract: OBJECTIVE
  To evaluate the causes of visual impairment and blindness in adult Chinese in an urban and rural region of Beijing, China.
  
  
  METHODS
  Population-based prevalence survey.
  
  
  METHODS
  From a rural region and an urban region of Greater Beijing, 4439 of 5324 > or=40-year-old invited subjects participated in the study (response rate, 83.4%). Using the World Health Organization (WHO) standard and the United States standard, blindness was defined as best-corrected visual acuity (BCVA) in the better-seeing eye of <20/400 and of <2/20, respectively, and visual impairment was defined as best-corrected vision of <20/60 and > or =20/400, and of <20/40 and > or =2/20, respectively.
  
  
  METHODS
  Determination of BCVA, pneumotonometry, frequency doubling perimetry, evaluation of photographs of the fundus and lens, and clinical examination.
  
  
  METHODS
  Causes of visual impairment and blindness.
  
  
  RESULTS
  Visual acuity measurements were available for 8816 eyes of 4409 subjects (99.3%). Using the WHO standard and the U.S. standard, 49 (1.1%) subjects and 95 (2.2%) subjects, respectively, had low vision, and 13 (0.3%) subjects and 15 (0.3%) subjects, respectively, were blind by definition. Taking the whole study population, the most frequent cause of low vision/blindness was cataract (36.7%/38.5%), followed by degenerative myopia (32.7%/7.7%), glaucoma (14.3%/7.7%), corneal opacity (6.1%/15.4%), and other optic nerve damage (2.0%/7.7%). Age-related macular degeneration (AMD) (2.0%/7.7%) and diabetic retinopathy (0%/7.7%) were responsible for a minority of cases. In subjects 40 to 49 years old, the most frequent cause of low vision and blindness was degenerative myopia. In the 50- to 59-year age group, the most frequent cause was cataract, followed by degenerative myopia. In the 60- to 69-year-old subjects and the > or =70-year group, the most frequent cause of low vision and blindness was cataract, followed by degenerative myopia and glaucoma.
  
  
  CONCLUSIONS
  The most frequent cause of low vision and blindness in adult Chinese is cataract, followed by degenerative myopia and glaucomatous optic neuropathy, with degenerative myopia dominating in younger groups and cataract dominating in elder groups. In contrast to studies in Western countries, AMD and diabetic retinopathy appear to play a minor role as a cause of visual impairment in elderly Chinese.
authors.affiliation: Department of Ophthalmology and Eye Hospital, Tongren Hospital, Beijing, China.
authors.forename: Liang
authors.initials: L
authors.lastname: Xu
authors.forename: Yaxing
authors.initials: Y
authors.lastname: Wang
authors.forename: Yibin
authors.initials: Y
authors.lastname: Li
authors.forename: Yun
authors.initials: Y
authors.lastname: Wang
authors.forename: Tongtong
authors.initials: T
authors.lastname: Cui
authors.forename: Jianjun
authors.initials: J
authors.lastname: Li
authors.forename: Jost B
authors.initials: JB
authors.lastname: Jonas
mesh_terms: D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D001766:Blindness / Q000453:epidemiology* / Q000209:etiology; D002386:Cataract / Q000150:complications / Q000453:epidemiology; D002681:China / Q000453:epidemiology; D005128:Eye Diseases / Q000150:complications* / Q000453:epidemiology; D005260:Female; D005901:Glaucoma / Q000150:complications / Q000453:epidemiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D047728:Myopia, Degenerative / Q000150:complications / Q000453:epidemiology; D009901:Optic Nerve Diseases / Q000150:complications / Q000453:epidemiology; D015995:Prevalence; D012424:Rural Population / Q000706:statistics & numerical data*; D017678:Sex Distribution; D014505:Urban Population / Q000706:statistics & numerical data*; D015354:Vision, Low / Q000453:epidemiology* / Q000209:etiology; D014792:Visual Acuity; D019987:Persons with Visual Disabilities / Q000706:statistics & numerical data*