title: [Relationship between pterygium onset and ultraviolet rays exposure time].
abstract: OBJECTIVE
  To investigate the dose-effect relationship between the radiation of ultraviolet ray and the onset of pterygium quantitatively.
  
  
  METHODS
  Interrogation was conducted to 95 patients with pterygium in Yacheng district, Sanya City, Hainan Province, 37 males and 58 females, aged 55.7 +/- 13.8 (20 - 80), and 95 local volunteers in 1:1 pairs matched in age, sex, race, and similar habits of wearing glasses and caps (control group). Both the pterygium group and control group were re-divided into three sub-groups: youth (aged < or = 40), middle-aged (aged 41 - 60), and elderly (aged > 60). The time of exposing to ultraviolet ray was calculated. Photo of the pterygium was taken. The length of the pterygium invading into cornea was measured.
  
  
  RESULTS
  The ultraviolet ray exposure time of the youth subgroup, pterygium group, was 35,637 +/- 13,587 hours, significantly higher than that of the youth subgroup, control group (26,188 +/- 17,423 hours, t = 3.352, P = 0.006). The ultraviolet ray exposure time of the middle-aged subgroup, pterygium group, was 73,412 +/- 23,082 hours, significantly higher than that of the middle-aged subgroup, control group (63,368 +/- 25,091 hours, t = 2.322, P = 0.024). However, there was no significant difference in the ultraviolet ray exposure time between the elderly subgroups of both groups. The length of the pterygium invading into cornea was positively correlated with the ultraviolet ray exposure time (r = 0.361, P < 0.05), and the length showed a trend of increased with aging.
  
  
  CONCLUSIONS
  There is a certain dose-effect correlation between ultraviolet ray exposure and the etiology of pterygium.
authors.affiliation: Department of Ophthalmology, Fourth Affiliated Hospital, China Medical University, Shenyang 110005, China.
authors.forename: Qi-chang
authors.initials: QC
authors.lastname: Yan
authors.forename: Zhong-xin
authors.initials: ZX
authors.lastname: Liu
authors.forename: Yue
authors.initials: Y
authors.lastname: Di
authors.forename: Wei
authors.initials: W
authors.lastname: Wang
authors.forename: Qian
authors.initials: Q
authors.lastname: Gao
authors.forename: Jin-song
authors.initials: JS
authors.lastname: Zhang
authors.forename: Yang
authors.initials: Y
authors.lastname: Liu
authors.forename: Rong
authors.initials: R
authors.lastname: Liu
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002681:China / Q000453:epidemiology; D004307:Dose-Response Relationship, Radiation; D004781:Environmental Exposure / Q000009:adverse effects*; D005260:Female; D006801:Humans; D008297:Male; D016555:Matched-Pair Analysis; D008875:Middle Aged; D011625:Pterygium / Q000453:epidemiology* / Q000209:etiology; D013997:Time Factors; D014466:Ultraviolet Rays / Q000009:adverse effects*