title: Prevalence of pterygium and cataract in indigenous populations of the Brazilian Amazon rain forest.
abstract: OBJECTIVE
  To compare the prevalence of pterygium and cataract in four indigenous populations of the Brazilian Amazonian rain forest (Arawak, Tukano, Maku, and Yanomami) with different ethnic and social behaviour backgrounds.
  
  
  METHODS
  A cross-sectional pterygium and cataract survey was performed in 624 adult Indians of the Brazilian rain forest belonging to four different ethnic groups. The Indians were classified according to their social behaviour in two groups: Arawak and Tukano (group 1) and Maku and Yanomami (group 2). Slit-lamp biomicroscopy was employed to examine the entire sample. All subjects were classified as 1 or 0 according to the presence or absence pterygium and cataract. Sex and age were also recorded.
  
  
  RESULTS
  chi(2)-tests revealed that the prevalence of pterygium and cataract differed significantly between groups 1 and 2. For pterygia: 36.6% (97/265) and 5.0% (18/359), respectively (chi(2)=101.2, P<0.0001), and for cataracts: 24.5% (65/265) and 13.7% (49/359) respectively (chi(2)=12.09, P=0.0005). Gender was not associated with pterygium (P=0.1326) and cataract (P=0.2263) in both groups. Elderly subjects showed a significantly higher prevalence of cataract (P<0.0001). The prevalence of pterygia did not increase with age (P=0.8079) in both groups.
  
  
  CONCLUSIONS
  Indians of group 1 have higher prevalence of pterygia and cataract than Indians of group 2. Social behaviour, especially the rate of sun exposure, appears to be the main factor for the different rates of pterygium and cataract displayed by these indigenous people of the Brazilian rain forest.
authors.affiliation: School of Medicine of Ribeirão Preto, USP, Brazil. jayterdepaula@yahoo.com.br
authors.forename: J S
authors.initials: JS
authors.lastname: Paula
authors.forename: F
authors.initials: F
authors.lastname: Thorn
authors.forename: A A V
authors.initials: AA
authors.lastname: Cruz
mesh_terms: D000328:Adult; D017677:Age Distribution; D000368:Aged; D001938:Brazil / Q000453:epidemiology; D002386:Cataract / Q000208:ethnology* / Q000209:etiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D011625:Pterygium / Q000208:ethnology* / Q000209:etiology; D011832:Radiation Injuries / Q000208:ethnology / Q000209:etiology; D017678:Sex Distribution; D013472:Sunlight / Q000009:adverse effects