title: Quantitative iris parameters and association with narrow angles.
abstract: OBJECTIVE
  To investigate the relationship between quantitative iris parameters (iris curvature [I-Curv], iris area [I-Area], and iris thickness) and the presence of narrow angles.
  
  
  METHODS
  Cross-sectional, community-based study.
  
  
  METHODS
  We recruited 2047 subjects >50 years old without ophthalmic symptoms from a community clinic in Singapore.
  
  
  METHODS
  All subjects underwent gonioscopy and anterior segment optical coherence tomography (AS-OCT) under dark conditions. An eye was considered to have narrow angles if the posterior pigmented trabecular meshwork was not visible for >/=180 degrees on nonindentation gonioscopy with the eye in the primary position. Customized software was used on horizontal AS-OCT scans to measure I-Curv, I-Area, and iris thickness 750 mum (IT750) and 2000 mum (IT2000) from the scleral spur. The average of both temporal and nasal measured values of the right eye was used for analysis.
  
  
  METHODS
  The association between iris parameters and narrow angles on gonioscopy.
  
  
  RESULTS
  Iris parameters from 1465 eyes (71.6%) were available for analysis. Of these, 315 subjects (21.5%) had narrow angles. The mean I-Curv (0.366 vs 0.259 mm; P<0.020), IT750 (0.476 vs 0.453 mm; P<0.001), and IT2000 (0.491 vs 0.482 mm; P = 0.010) were greater in persons with than without narrow angles. After adjusting for age, gender, anterior chamber depth, axial length, and pupil size, the greater I-Curv, I-Area, IT750, and IT2000 were significantly associated with narrow angles (odds ratio [OR] 2.5 and 95% confidence interval [CI], 1.3-5.1; OR, 2.7 and 95% CI, 1.6-4.8; OR, 2.6 and 95% CI, 1.6-4.1; OR, 2.7 and 95% CI, 1.5-4.7, comparing 4th with 1st quartile for each parameter, respectively). In stratified analysis, women and subjects aged >/=60 years had stronger associations for most iris parameters with narrow angles than men and younger subjects.
  
  
  CONCLUSIONS
  Quantitative iris parameters (I-Curv, I-Area, and iris thickness) are independently associated with narrow angles, particularly in women and older subjects. These data provide further insights into the pathogenesis of angle closure in Singaporeans.
  
  
  BACKGROUND
  Proprietary or commercial disclosure may be found after the references.
authors.affiliation: Singapore Eye Research Institute and Singapore National Eye Center, Singapore.
authors.forename: Bingsong
authors.initials: B
authors.lastname: Wang
authors.forename: Lisandro M
authors.initials: LM
authors.lastname: Sakata
authors.forename: David S
authors.initials: DS
authors.lastname: Friedman
authors.forename: Yiong-Huak
authors.initials: YH
authors.lastname: Chan
authors.forename: Mingguang
authors.initials: M
authors.lastname: He
authors.forename: Raghavan
authors.initials: R
authors.lastname: Lavanya
authors.forename: Tien-Yin
authors.initials: TY
authors.lastname: Wong
authors.forename: Tin
authors.initials: T
authors.lastname: Aung
mesh_terms: D000869:Anterior Eye Segment / Q000473:pathology; D019540:Area Under Curve; D003430:Cross-Sectional Studies; D004108:Dilatation, Pathologic; D005189:False Positive Reactions; D005260:Female; D015812:Glaucoma, Angle-Closure / Q000175:diagnosis / Q000209:etiology*; D006068:Gonioscopy; D006801:Humans; D007429:Intraocular Pressure; D007498:Iris / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012307:Risk Factors; D012680:Sensitivity and Specificity; D011795:Surveys and Questionnaires; D041623:Tomography, Optical Coherence; D014065:Tonometry, Ocular