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Association of iris surface features with iris parameters assessed by swept-source optical coherence tomography in Asian eyes
  1. Tin A Tun1,
  2. Jacqueline Chua1,2,
  3. Yuan Shi1,
  4. Elizabeth Sidhartha1,
  5. Sri Gowtham Thakku1,
  6. William Shei1,
  7. Marcus Chiang Lee Tan1,3,
  8. Joanne Hui Min Quah4,
  9. Tin Aung1,2,5,
  10. Ching-Yu Cheng1,2,5
  1. 1Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore
  2. 2Ophthalmology and Visual Sciences Academic Clinical Program, Duke-NUS Medical School, Singapore, Singapore
  3. 3Ophthalmology Service, Jurong Health Service, Singapore, Singapore
  4. 4SingHealth Polyclinics, Outram, Singapore, Singapore
  5. 5Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
  1. Correspondence to Dr Ching-Yu Cheng, Singapore Eye Research Institute, 20 College Road, Academia, Level 6, Discovery Tower, Singapore 169856, Singapore; chingyu.cheng{at}duke-nus.edu.sg

Abstract

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.

  • Iris
  • Epidemiology
  • Glaucoma
  • Imaging

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