Associations of iris structural measurements in a Chinese population: the Singapore Chinese Eye Study

We determined the ocular biometric and demographic factors associated with iris parameters in Singaporean Chinese persons from a population-based sample.

Subjects were participants in the Singapore Chinese Eye Study, a population-based cross-sectional study of eye disease. Anterior segment optical coherence tomography images were analyzed using customized software to measure iris thickness at 750 μm from the scleral spur (IT750), iris area (I-Area), and iris curvature (I-Curv). Regression analyses were performed to assess the association between iris measurements with a range of demographic and ocular variables. The contribution of each independent variable to the iris parameter of interest was determined sequentially using a stepwise selection algorithm.

We included 1473 participants with a mean age of 57.7 + 8.68 years, and 50.6% were men. The mean IT750, I-Area, and I-Curv were 0.46 ± 0.10 mm, 1.49 ± 0.24 mm(2), and 0.25 ± 0.13 mm, respectively. Statistical regression models, including a range of demographic and ocular parameters, explained 59.3%, 41.9%, and 34.3% of the variability in I-Curv, IT750, and I-Area, respectively. Angle opening distance at 750 μm from the scleral spur (AOD750) was the single factor associated most strongly with I-Curv, and explained 46.6% of its variation.

A significant proportion of the variation in iris area, curvature, and thickness was not explained by other ocular and demographic parameters. Iris curvature was associated strongly with angle width, and of all parameters investigated, AOD750 was most highly correlated with iris curvature.