title: Assessment of iris surface features and their relationship with iris thickness in Asian eyes.
abstract: OBJECTIVE
  To assess iris surface features in Asian eyes and examine their associations with iris thickness measured by anterior segment optical coherence tomography (AS OCT).
  
  
  METHODS
  Cross-sectional study.
  
  
  METHODS
  We recruited 250 subjects from the Singapore Malay Eye Study.
  
  
  METHODS
  We obtained standardized slit-lamp photographs and developed a grading system assessing iris crypts (by number and size), furrows (by number and circumferential extent), and color (higher grade denoting darker iris). Vertical and horizontal cross-sections of the anterior chamber were imaged using AS OCT. Intragrader and intergrader agreements in the grading of iris surface were assessed by weighted κ (κ(w)) statistic. Associations of the average iris thickness with the grade of iris features were assessed using linear regression analysis.
  
  
  METHODS
  Frequency and size of iris crypts, furrows, and color; iris thickness at 750 μm (IT750) and 2000 μm (IT2000) from the scleral spur; and maximum iris thickness (ITM) averaged from the 4 quarters.
  
  
  RESULTS
  Three hundred sixty-four eyes had complete and gradable data for crypts and color; 330 eyes were graded for furrows. The grading scheme showed good intragrader (crypt κ(w) = 0.919, furrow κ(w) =0.901, color κ(w) = 0.925) and intergrader (crypt κ(w) = 0.775, furrow κ(w) = 0.836, color κ(w) = 0.718) agreements. Higher crypt grade was associated independently with thinner IT750 (β [change in iris thickness per grade higher] = -0.007; P = 0.029), IT2000 (β = -0.018; P < 0.001), and ITM (β = -0.012; P < 0.001). More extensive furrows were associated with thicker IT750 (β = 0.022; P < 0.001). Darker iris was also associated with thicker IT750 (β = 0.014; P = 0.001).
  
  
  CONCLUSIONS
  Iris surface features, assessed and measured from slit-lamp photographs, correlate well with iris thickness. Irises with more crypts are thinner; irises with more extensive furrows and darker color are thicker peripherally. These findings may provide another means to assess angle closure risk based on iris features.
authors.affiliation: Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Republic of Singapore; Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore and National University Health System, Singapore, Republic of Singapore.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Sidhartha
authors.affiliation: Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Republic of Singapore; Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore and National University Health System, Singapore, Republic of Singapore.
authors.forename: Preeti
authors.initials: P
authors.lastname: Gupta
authors.affiliation: Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Republic of Singapore.
authors.forename: Jiemin
authors.initials: J
authors.lastname: Liao
authors.affiliation: Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Republic of Singapore; Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore and National University Health System, Singapore, Republic of Singapore.
authors.forename: Yih-Chung
authors.initials: YC
authors.lastname: Tham
authors.affiliation: Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Republic of Singapore; Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore and National University Health System, Singapore, Republic of Singapore; Centre for Quantitative Medicine, Office of Clinical Sciences, Duke-NUS Graduate Medical School, Singapore, Republic of Singapore.
authors.forename: Carol Y
authors.initials: CY
authors.lastname: Cheung
authors.affiliation: State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China.
authors.forename: Mingguang
authors.initials: M
authors.lastname: He
authors.affiliation: Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Republic of Singapore; Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore and National University Health System, Singapore, Republic of Singapore.
authors.forename: Tien Y
authors.initials: TY
authors.lastname: Wong
authors.affiliation: Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Republic of Singapore; Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore and National University Health System, Singapore, Republic of Singapore.
authors.forename: Tin
authors.initials: T
authors.lastname: Aung
authors.affiliation: Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Republic of Singapore; Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore and National University Health System, Singapore, Republic of Singapore; Centre for Quantitative Medicine, Office of Clinical Sciences, Duke-NUS Graduate Medical School, Singapore, Republic of Singapore; Saw Swee Hock School of Public Health, National University of Singapore and National University Health System, Singapore, Republic of Singapore. Electronic address: ching-yu_cheng@nuhs.edu.sg.
authors.forename: Ching-Yu
authors.initials: CY
authors.lastname: Cheng
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D044466:Asian People / Q000208:ethnology; D003430:Cross-Sectional Studies; D005127:Eye Color; D005260:Female; D006801:Humans; D007498:Iris / Q000033:anatomy & histology*; D008297:Male; D008875:Middle Aged; D009929:Organ Size; D010781:Photography; D011446:Prospective Studies; D012846:Singapore; D041623:Tomography, Optical Coherence