title: Differences in iris structural measurements among American Caucasians, American Chinese and mainland Chinese.
abstract: BACKGROUND
  To assess the distribution of iris structural measurements among American Caucasians, American Chinese and mainland Chinese aged 40years and over, in order to determine associated factors of increased risk for angle closure in Chinese.
  
  
  METHODS
  Prospective multicentre cross-sectional study.
  
  
  METHODS
  Four gender- and age-matched cohorts: Caucasians, American Chinese, Southern Chinese from Guangzhou and Northern Chinese from Beijing were enrolled in this study.
  
  
  METHODS
  Anterior segment optical coherence tomography was utilized to image the anterior chamber. Customized software was used to calculate the related parameters from anterior segment optical coherence tomography images.
  
  
  METHODS
  Iris thickness at 750µm from the scleral spur, iris curvature, iris area, pupil diameter.
  
  
  RESULTS
  Data from 121, 124, 121 and 120 subjects were available for American Caucasian, American Chinese, Southern and Northern Mainland Chinese subjects, respectively. The Chinese cohorts did not differ with regard to any of the parameters. Multiple linear regressions indicated that Caucasians had thinner iris thickness at 750µm from the scleral spur and smaller iris area than Chinese after controlling for potential confounders. Female Caucasians had thinner irides (P=0.015) and smaller iris area (P=0.001) than male Caucasians. Female Chinese tended to have more convex irides (P=0.021) than male Chinese. Pupil size was inversely associated with age (P<0.001) in both ethnicities.
  
  
  CONCLUSIONS
  In dark conditions, Chinese have thicker irides and greater iris area than Caucasians independent of pupil size. Among Chinese, more convex irides in women may account for the higher rate of narrow angles identified in this segment of the Chinese population.
authors.affiliation: State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China.
authors.forename: Dandan
authors.initials: D
authors.lastname: Wang
authors.forename: Mingguang
authors.initials: M
authors.lastname: He
authors.forename: Lingling
authors.initials: L
authors.lastname: Wu
authors.forename: Stephanie
authors.initials: S
authors.lastname: Yaplee
authors.forename: Kuldev
authors.initials: K
authors.lastname: Singh
authors.forename: Shan
authors.initials: S
authors.lastname: Lin
mesh_terms: D000328:Adult; D000368:Aged; D001213:Asian / Q000208:ethnology*; D044466:Asian People / Q000208:ethnology*; D002681:China / Q000453:epidemiology; D003430:Cross-Sectional Studies; D005260:Female; D015812:Glaucoma, Angle-Closure / Q000208:ethnology; D006801:Humans; D007498:Iris / Q000033:anatomy & histology*; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011680:Pupil / Q000502:physiology*; D012307:Risk Factors; D041623:Tomography, Optical Coherence; D014481:United States / Q000453:epidemiology; D044465:White People / Q000208:ethnology*