Peer-reviewed

Assessment of Iris Surface Features and Their Relationship with Iris Thickness in Asian Eyes – Corrected Proof

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Purpose: To assess iris surface features in Asian eyes and examine their associations with iris thickness measured by anterior segment optical coherence tomography (AS OCT).Design: Cross-sectional study.Participants: 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 (κw) statistic. Associations of the average iris thickness with the grade of iris features were assessed using linear regression analysis.Main Outcome Measures: 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 κw = 0.919, furrow κw =0.901, color κw = 0.925) and intergrader (crypt κw = 0.775, furrow κw = 0.836, color κw = 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.