title: Association of iris surface features with iris parameters assessed by swept-source optical coherence tomography in Asian eyes.
abstract: OBJECTIVE
  To characterise the association of iris surface features (crypts, furrows and colour) with iris volume and curvature assessed by swept-source optical coherence tomography (SSOCT) in Asian eyes.
  
  
  METHODS
  Iris crypts (by number and size) and furrows (by number and circumferential extent) were graded from iris photographs. Iris colour was measured by a customised algorithm written on MATLAB (MathWorks, Natick, Massachusetts, USA). The iris was imaged by SSOCT (SS-1000, CASIA, Tomey, Nagoya, Japan). The associations of surface features with iris parameters were analysed using a generalised estimating equation.
  
  
  RESULTS
  A total of 1704 subjects (3297 eyes) were included in the analysis. The majority was Chinese (86.4%), and 63.2% were females, and their mean age (±SD) was 61.4±6.6 years. After adjusting for age, sex, ethnicity, pupil size and corneal arcus, higher iris crypt grade was independently associated with smaller iris volume (β=-0.54, p<0.001), whereas darker irides and higher iris furrow grade were associated with larger iris volume (β=-0.041, p<0.001) and (β=0.233, p<0.001), respectively. Lighter coloured irides with more crypts and/or more furrows were also associated with less convexity (crypts: β=-0.003, p=0.03; furrows: β=-0.004, p=0.007; and colour: β=-0.001, p=0.005).
  
  
  CONCLUSIONS
  Iris surface features were highly correlated with iris volume and curvature. Irides with more crypts have a smaller volume; and darker irides with more furrows have a larger volume. Lighter irides with more crypts and/or furrows have less convexity.
authors.affiliation: Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore.
authors.forename: Tin A
authors.initials: TA
authors.lastname: Tun
authors.affiliation: Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore.|Ophthalmology and Visual Sciences Academic Clinical Program, Duke-NUS Medical School, Singapore, Singapore.
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Chua
authors.affiliation: Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Shi
authors.affiliation: Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Sidhartha
authors.affiliation: Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore.
authors.forename: Sri Gowtham
authors.initials: SG
authors.lastname: Thakku
authors.affiliation: Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore.
authors.forename: William
authors.initials: W
authors.lastname: Shei
authors.affiliation: Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore.|Ophthalmology Service, Jurong Health Service, Singapore, Singapore.
authors.forename: Marcus Chiang Lee
authors.initials: MC
authors.lastname: Tan
authors.affiliation: SingHealth Polyclinics, Outram, Singapore, Singapore.
authors.forename: Joanne Hui Min
authors.initials: JH
authors.lastname: Quah
authors.affiliation: Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore.|Ophthalmology and Visual Sciences Academic Clinical Program, Duke-NUS Medical School, Singapore, Singapore.|Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore.
authors.forename: Tin
authors.initials: T
authors.lastname: Aung
authors.affiliation: Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore.|Ophthalmology and Visual Sciences Academic Clinical Program, Duke-NUS Medical School, Singapore, Singapore.|Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore.
authors.forename: Ching-Yu
authors.initials: CY
authors.lastname: Cheng
mesh_terms: D003430:Cross-Sectional Studies; D005260:Female; D005500:Follow-Up Studies; D015812:Glaucoma, Angle-Closure / Q000175:diagnosis / Q000453:epidemiology*; D006068:Gonioscopy; D006801:Humans; D015994:Incidence; D007429:Intraocular Pressure / Q000502:physiology; D007498:Iris / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012846:Singapore / Q000453:epidemiology; D041623:Tomography, Optical Coherence / Q000379:methods*
keywords: Epidemiology; Glaucoma; Imaging; Iris