Purpose.: A pilot study to analyze the association of change in iris parameters with physiological mydriasis in angle closure eyes compared with normal control eyes among south Indian participants. Methods.: Sixteen eyes diagnosed with primary angle closure and 14 age, gender-matched open-angle control eyes were selected. All participants underwent anterior segment imaging using anterior segment optical coherence tomography in dim and bright illumination. The iris area (IA), iris volume (IV), and pupillary diameter were calculated using customized image processing software. Results.: The IA and IV were found to be lesser in angle closure compared with normal controls. Average IA (dim and bright) was found to be 3.4 and 3.7 mm 2 in normals and 3.03 and 3.35 mm 2 in angle closure, and average IV (dim and bright) was found to be 24.28 and 26.09 mm 3 in normals and 21.38 and 22.6 mm 3 in angle closure. The IA and IV decreased significantly with pupillary dilation in normals and in angle closures. However, decrease in the IA (slope = 0.52 and 0.42; p = 0.012) and IV (slope = 1.97 and 1.41; p = 0.014) with pupillary dilation was significantly higher in normals compared with angle closures, respectively. Conclusions.: IA and IV were found to decrease as pupil dilates in normal and angle closure eyes among South Indians. Loss in the IV was found to be lower in angle closure eyes.
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