title: Pterygium in Tibetans: a population-based study in China.
abstract: OBJECTIVE
  To describe the prevalence and to identify associated risk factors for pterygium in a Tibetan population at high altitude in Zeku County, China.
  
  
  METHODS
  A prospective population-based survey was conducted from October to December 2006. A stratified, clustered, randomized sampling procedure was used to select 2632 Tibetan people aged 40 years and older. Pterygium was diagnosed and graded clinically as grade 1 (transparent), 2 (intermediate) and 3 (opaque). Risks factors associated with pterygium were evaluated with logistic regression models.
  
  
  RESULTS
  From a total of 2632 eligible subjects, 2229 (84.69%) were examined. There were 323 people with pterygium, equivalent to an overall prevalence of 14.49% (95% confidence interval [CI] 13.03-15.95). Pterygium was independently associated with increasing age for persons aged 70-79 years, compared with those aged 40-49 years (odds ratio [OR] 2.0; 95% CI 1.4-2.8), female gender (OR 1.6; 95% CI 1.2-2.0), dry eye symptoms (OR 1.3; 95% CI 1.0-1.7), seldom use of sunglasses/crystal spectacles (OR 4.6; 95% CI 1.9-11.3) or hats (OR 3.6: 95% CI 2.4-5.4), lower education level (<3 years) (OR 1.6; 95% CI 1.1-2.4) and low socioeconomic status (OR 1.9; 95% CI 1.5-2.4).
  
  
  CONCLUSIONS
  The prevalence of pterygium in a Tibetan population at high altitude is significantly high, particularly in certain at-risk groups. The primary causative factors are related to ocular sun exposure, which are easily preventable. Public health schemes to address this serious health issue are urgently needed.
authors.affiliation: Ophthalmology Department, West China Hospital, Sichuan University, Chengdu, Sichuan Province, China.
authors.forename: Peng
authors.initials: P
authors.lastname: Lu
authors.forename: Xiaoming
authors.initials: X
authors.lastname: Chen
authors.forename: Ying
authors.initials: Y
authors.lastname: Kang
authors.forename: Lang
authors.initials: L
authors.lastname: Ke
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Wei
authors.forename: Wenfang
authors.initials: W
authors.lastname: Zhang
mesh_terms: D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D004522:Educational Status; D005139:Eyeglasses / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D011446:Prospective Studies; D011481:Protective Clothing / Q000706:statistics & numerical data; D011625:Pterygium / Q000453:epidemiology* / Q000209:etiology*; D011835:Radiation Protection / Q000379:methods; D012307:Risk Factors; D017678:Sex Distribution; D012923:Social Class; D013472:Sunlight; D018609:Tibet / Q000453:epidemiology