title: [Causes of moderate to severe visual impairment and blindness in population aged 50 years or more in rural Shandong province].
abstract: OBJECTIVE
  To investigate the etiological spectrum of moderate to severe visual impairment and blindness in population aged 50 years or more in rural Shandong province, China.
  
  
  METHODS
  A population based, random cluster sampling was used to screening the adults aged 50 years or more living in rural Shandong Province from April to July 2008. Three counties and one suburb representing the different levels of socioeconomic development within Shandong area were selected as the investigated areas. Geographically defined cluster sampling was used in randomly selecting a cross-section of residents aged ≥ 50 years from each county. Best corrected visual acuity and intra-ocular pressure were evaluated in those with presenting visual acuity ≤ 0.5 and suspected glaucoma respectively. The major causes of visual impairment and blindness were diagnosed in those with presenting visual acuity ≤ 0.3. According to the results of presenting visual acuity and best corrected visual acuity, the etiology constituent ratios of the moderate to severe visual impairment and blindness were analyzed respectively.
  
  
  RESULTS
  According to the number of people, the first three principal causes for blindness based on the presenting visual acuity were cataract (59.8%, 168/281), fundus disease (12.1%, 34/281) and corneal opacity (4.3%, 12/281) or ametropia (4.3%, 12/281). The first three principal causes for moderate to severe visual impairment and blindness were cataract (55.2%, 844/1530), uncorrected refractive error (18.2%, 278/1530) and fundus disease (11.9%, 182/1530). Based on the best corrected visual acuity, the first three principal causes for blindness were cataract (64.6%, 153/237), fundus disease (10.5%, 25/237) and corneal opacity (4.7%, 11/237), respectively. The first three principal causes for moderate to severe visual impairment and blindness were cataract (66.4%, 590/889), fundus disease (16.0%, 142/889) and optic nerve atrophy (3.0%, 27/889). According to number of the eyes, proportion of cataract in cases with moderate to severe visual impairment and blindness had positive relation with age, the proportion of ametropia and fundus disease had negative relation with age. The etiology constituent ratio had no difference between male and female. The proportion of cataract in cases with moderate to severe visual impairment and blindness in Huaiyin District of Jinan was slightly lower than those in other areas, however, the proportion ratio of ametropia and fundus disease was slightly higher than those in other areas.
  
  
  CONCLUSIONS
  Cataract, uncorrected refractive error, and fundus diseases are ranked in the top three causes of moderate to severe visual impairment and blindness in adults aged 50 years or more in rural Shandong Province.
authors.affiliation: Department of Ophthalmology, Provincial Hospital Affiliated to Shandong University, Jinan, China.
authors.forename: Yun
authors.initials: Y
authors.lastname: Li
authors.forename: Hong-sheng
authors.initials: HS
authors.lastname: Bi
authors.forename: Li-hua
authors.initials: LH
authors.lastname: Wang
authors.forename: Ting
authors.initials: T
authors.lastname: Wang
authors.forename: Shao-yuan
authors.initials: SY
authors.lastname: Yang
authors.forename: Li-ping
authors.initials: LP
authors.lastname: Liu
authors.forename: Cheng-chao
authors.initials: CC
authors.lastname: Zhou
mesh_terms: D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D001766:Blindness / Q000453:epidemiology*; D002681:China / Q000453:epidemiology; D005128:Eye Diseases / Q000453:epidemiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012030:Refractive Errors / Q000453:epidemiology; D012424:Rural Population; D014786:Vision Disorders / Q000453:epidemiology*