Purpose:
To assess the iris movement under the dark and light changes.
Methods:
10 healthy subjects and 10 primary angle closure glaucoma (PACG) patients were recruited from National University Hospital (NUH) glaucoma clinic. The dynamic videos of iris movement in response to dark-light illumination changes were captured using AS-OCT (Carl Zess, US). The videos were analysed by frames and a program was used to resize and dewarp each frame (Matlab, US). Frame images were then analysed by customized program. Iris movement parameters, such as IMT (iris movement time), IMD (iris movement distance), IMS (iris movement speed), were measured and t test was used to find the difference between the two groups.
Results:
In response to illumination changes, PACG patients took a longer time for pupil miosis compared to healthy (0.986±0.219second vs1.600±0.355second, p=0.003). The IMD for both nasal and temporal iris did not show any significant difference between control and PACG groups (nasal 0.915±0.358mm vs 1.107±0.423mm; p=0.228; temporal 0.943±0.324mm vs 1.181±0.337mm p=0.143). Iris movement was faster in the control group than PACG group for temporal (0.946±0.194mm/sec vs 0.741±0.164mm/sec, p=0.048) and nasal sides (0.917±0.230mm/sec vs 0.675±0.16mm/sec, p=0.016).
Conclusions:
In this pilot study, the iris movement of healthy subjects was faster than PACG patients in response to changes in illumination. There was no significant difference in iris movement distance between healthy subjects and PACG patients.
Keywords: imaging/image analysis: clinical • image processing • pupillary reflex