Abstract
PurposeDefine criteria for iris-related parameters in an adult open angle population as measured with swept source Fourier domain anterior segment optical coherence tomography (ASOCT).MethodsNinety-eight eyes of 98 participants with open angles were included and stratified into 5 age groups (18–35, 36–45, 46–55, 56–65, and 66–79 years). ASOCT scans with 3D mode angle analysis were taken with the CASIA SS-1000 (Tomey Corporation, Nagoya, Japan) and analyzed using the Anterior Chamber Analysis and Interpretation software. Anterior iris surface length (AISL), length of scleral spur landmark (SSL) to pupillary margin (SSL-to-PM), iris contour ratio (ICR = AISL/SSL-to-PM), pupil radius, radius of iris centroid (RICe), and iris volume were measured. Outcome variables were summarized for all eyes and age groups, and mean values among age groups were compared using one-way analysis of variance. Stepwise regression analysis was used to investigate demographic and ocular characteristic factors that affected each iris-related parameter.ResultsMean (±SD) values were 2.24 mm (±0.46), 4.06 mm (±0.27), 3.65 mm (±0.48), 4.16 mm (±0.47), 1.14 (±0.04), 1.51 mm2 (±0.23), and 38.42 μL (±4.91) for pupillary radius, RICe, SSL-to-PM, AISL, ICR, iris cross-sectional area, and iris volume, respectively. Both pupillary radius (P = 0.002) and RICe (P = 0.027) decreased with age, while SSL-to-PM (P = 0.002) and AISL increased with age (P = 0.001). ICR (P = 0.54) and iris volume (P = 0.49) were not affected by age.ConclusionThis study establishes reference values for iris-related parameters in an adult open angle population, which will be useful for future studies examining the role of iris changes in pathologic states.
Highlights
Changes in iris from light to dark play an important role in the pathogenesis of primary angle closure (PAC)
Mean (±standard deviation (SD)) values were 2.24 mm (±0.46), 4.06 mm (±0.27), 3.65 mm (±0.48), 4.16 mm (±0.47), 1.14 (±0.04), 1.51 mm2 (±0.23), and 38.42 μL (±4.91) for pupillary radius, radius of iris centroid (RICe), scleral spur landmark (SSL)-to-PM, Anterior iris surface length (AISL), iris contour ratio (ICR), iris cross-sectional area, and iris volume, respectively. Both pupillary radius (P = 0.002) and RICe (P = 0.027) decreased with age, while SSL-to-PM (P = 0.002) and AISL increased with age (P = 0.001)
This study establishes reference values for iris-related parameters in an adult open angle population, which will be useful for future studies examining the role of iris changes in pathologic states
Summary
Changes in iris from light to dark play an important role in the pathogenesis of primary angle closure (PAC). Though Aptel et al recently estimated iris volume using 2 sets of ASOCT scans of 2 meridians [2], the device must be reset between scans, and the accuracy of such measurements is limited by this delay. Narawanaswamy et al demonstrated an increase in iris cross-sectional area and a decrease in iris volume from light to dark in patients with PAC [3]; ASOCT iris measurements in this study were estimated using scans at only 4 meridians. Newer generation ASOCT instruments, such as the CASIA SS-1000 (Tomey Corporation, Nagoya, Japan), utilize swept source Fourier domain technology, allowing imaging of 128 meridians (256 angles) in 2.4 seconds [4, 5], producing rapid and high resolution measurements of the entire iris
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