Background/aims 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.
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Contributors Design of study: MCLT, JHMQ, TA, C-YC; conduct of the study: TAT, JC, WS, MT; collection and management of data: TAT, JC, ES, SGT; analysis and Interpretation of data: TAT, JC, YS; preparation of manuscript: TAT, JC, TA, C-YC; review or approval of manuscript: JC, MCLT, JHMQ, TA, C-YC.
Funding National Medical Research Council (NIG/1069/2012 and CIRG15may030).
Competing interests C-YC is supported by National Medical Research Council (CSA/033/2012).
Patient consent Obtained.
Ethics approval The study was approved by the SingHealth Centralised Institutional Review Board, and adhered to the tenets of the Declaration of Helsinki.
Provenance and peer review Not commissioned; externally peer reviewed.