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

  • Elizabeth Sidhartha
    Affiliations
    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
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  • Preeti Gupta
    Affiliations
    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
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  • Jiemin Liao
    Affiliations
    Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Republic of Singapore
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  • Yih-Chung Tham
    Affiliations
    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
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  • Carol Y. Cheung
    Affiliations
    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
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  • Mingguang He
    Affiliations
    State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China
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  • Tien Y. Wong
    Affiliations
    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
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  • Tin Aung
    Affiliations
    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
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  • Ching-Yu Cheng
    Correspondence
    Correspondence: Ching-Yu Cheng, MD, PhD, Department of Ophthalmology, National University Health System, 1E Kent Ridge Road, NUHS Tower Block Level 7, Singapore 119228, Republic of Singapore.
    Affiliations
    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
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Published:January 08, 2014DOI:https://doi.org/10.1016/j.ophtha.2013.11.028

      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 (κ w) 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 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.
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