Duration 5min, Q&A 3min
Interrelation Between Iris Thickness and Anterior Segment Biometric Parameters in Relation to Physiological Pupil Dilation in Eyes with Angle Closure and Those with Open Angle
Primary angle closure glaucoma is a significant cause of blindness in Asia. Assessment of angle configuration is important for the prevention and treatment of primary angle closure glaucoma. The purpose of this study was to investigate the associations among anterior segment biometric parameters in relation to physiological pupil dilation with light-dark changes, and to identify specific features that distinguish eyes with angle closure from those with open angle.
We used anterior segment optical coherence tomography (AS-OCT) to examine 118 eyes of 118 patients with angle closure (27 men and 91 women; mean age, 71.1 ± 8.3 years; classification: primary angle closure suspect [n = 65], primary angle closure [n = 40], primary angle closure glaucoma [n = 13]) and 40 eyes of 40 patients with primary open angle glaucoma (21 men and 19 women; mean age, 67.0 ± 8.7 years) under dark and light conditions.
We measured the iris thickness (IT), iris convexity (IC), anterior chamber depth (ACD), pupil diameter (PD), anterior chamber width (ACW), and crystalline lens rise (CLR), and analyzed the statistical difference between the angle closure and open angle groups. Additionally, we performed univariate analyses for IT in each group under both dark and light conditions and compared the dynamic change in relation to physiological pupil dilation with light-dark changes in both the groups.
Results and Conclusion
AS-OCT parameters of the angle closure group, except for IT, differed significantly from the open angle group under both dark and light conditions. In the angle closure group, IT showed a significant positive association with PD and negative association with IC under both dark (r = -0.391, p < 0.001) and light (r = -0.403, p < 0.001) conditions, and either did not have any significant association or had low correlation with the other AS-OCT parameters. In contrast, in the open angle group, IT was not significantly associated with any of the AS-OCT parameters.
With respect to pupil dilation, increase in the forward bowing of the iris had a positive influence on the decrease in iris thickness in the angle closure group, but not in the open angle group. These results indicate that the relative pupillary block exerts a greater stretching force on the iris in eyes with angle closure than in those with open angle, thus affecting iris thickness.
[ Keyword ]
angle closure / iris thickness / iris convexity / pupillary block / anterior segment coherence tomography
[ Conflict of Interest ]