title: Associations of iris structural measurements in a Chinese population: the Singapore Chinese Eye Study.
abstract: OBJECTIVE
  We determined the ocular biometric and demographic factors associated with iris parameters in Singaporean Chinese persons from a population-based sample.
  
  
  METHODS
  Subjects were participants in the Singapore Chinese Eye Study, a population-based cross-sectional study of eye disease. Anterior segment optical coherence tomography images were analyzed using customized software to measure iris thickness at 750 μm from the scleral spur (IT750), iris area (I-Area), and iris curvature (I-Curv). Regression analyses were performed to assess the association between iris measurements with a range of demographic and ocular variables. The contribution of each independent variable to the iris parameter of interest was determined sequentially using a stepwise selection algorithm.
  
  
  RESULTS
  We included 1473 participants with a mean age of 57.7 + 8.68 years, and 50.6% were men. The mean IT750, I-Area, and I-Curv were 0.46 ± 0.10 mm, 1.49 ± 0.24 mm(2), and 0.25 ± 0.13 mm, respectively. Statistical regression models, including a range of demographic and ocular parameters, explained 59.3%, 41.9%, and 34.3% of the variability in I-Curv, IT750, and I-Area, respectively. Angle opening distance at 750 μm from the scleral spur (AOD750) was the single factor associated most strongly with I-Curv, and explained 46.6% of its variation.
  
  
  CONCLUSIONS
  A significant proportion of the variation in iris area, curvature, and thickness was not explained by other ocular and demographic parameters. Iris curvature was associated strongly with angle width, and of all parameters investigated, AOD750 was most highly correlated with iris curvature.
authors.affiliation: Singapore Eye Research Institute and Singapore National Eye Centre, Singapore.
authors.forename: Chelvin C
authors.initials: CC
authors.lastname: Sng
authors.forename: John C
authors.initials: JC
authors.lastname: Allen
authors.forename: Monisha E
authors.initials: ME
authors.lastname: Nongpiur
authors.forename: Li-Lian
authors.initials: LL
authors.lastname: Foo
authors.forename: Yingfeng
authors.initials: Y
authors.lastname: Zheng
authors.forename: Carol Y
authors.initials: CY
authors.lastname: Cheung
authors.forename: Mingguang
authors.initials: M
authors.lastname: He
authors.forename: David S
authors.initials: DS
authors.lastname: Friedman
authors.forename: Tien Y
authors.initials: TY
authors.lastname: Wong
authors.forename: Tin
authors.initials: T
authors.lastname: Aung
mesh_terms: D000368:Aged; D000465:Algorithms; D016477:Artifacts; D044466:Asian People / Q000706:statistics & numerical data*; D001699:Biometry; D003430:Cross-Sectional Studies; D005260:Female; D015812:Glaucoma, Angle-Closure / Q000208:ethnology* / Q000473:pathology*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000592:standards / Q000706:statistics & numerical data; D007498:Iris / Q000033:anatomy & histology / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D015995:Prevalence; D012016:Reference Values; D012044:Regression Analysis; D015203:Reproducibility of Results; D012846:Singapore / Q000453:epidemiology; D041623:Tomography, Optical Coherence / Q000592:standards / Q000706:statistics & numerical data*