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Kyung Rim Sung, Jung Woo Cho, Youngrok Lee, Jung Hwa Na; Comparison Of Dynamic Iris Cross-sectional Area Change In Narrow Angle Eyes With Open Angle eyes Using Anterior Segment Optical Coherence Tomography. Invest. Ophthalmol. Vis. Sci. 2011;52(14):3026.
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Iris cross-sectional area is known to decrease with pupil dilation. We intended to evaluate the dynamic change of iris cross-sectional area due to pupil size change using anterior segment optical coherence tomography (AS OCT). We compared the dynamic iris cross-sectional area changes of primary angle closure suspect (PACS) with those of open angle eyes.
Fifty six open angle eyes and 66 PACS eyes were imaged by AS OCT (Visante, version 2.0, Carl Zeiss Meditec. Inc., CA, USA), enhanced anterior segment single mode (scan length 16mm; 256 A-scans). Among 66 PACS eyes, 6 eyes (9%) were fellow eyes of angle closure attack. AS OCT imaging was performed at 4 different standardized lighting conditions. The nasal and temporal cross-sectional iris area and pupil distance at 4 different lighting conditions was measured with Image J software (version 1.43u). Linear regression analysis of each eye was performed to find the rate of iris cross-sectional area change over pupil distance change. Correlation between anterior chamber depth (ACD) and the rate of iris cross-sectional area change over pupil distance change was sought.
Both open angle eyes and PACS eyes showed decrease of iris cross-sectional area according to pupil dilation. Mean rate of iris cross-sectional area change over pupil dilation was -0.0675±0.069 in open angle eyes, -0.041±0.028 in PACS eyes. PACS eyes showed significant less change of iris cross-sectional area according to pupil dilation (p=0.012). The ACD was not correlated with rate of iris cross-sectional area change in both open angle eyes and PACS eyes (p=0.37, 0.83).
The iris cross-sectional area decreased as pupil dilated in all eyes. However, PACS eyes showed significant less amount of change according to pupil dilation than open angle eyes. Reduction of iris area change according to pupil dilation may contribute to angle closure pathogenesis.
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