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Title: In vivo analysis of vectors involved in pupil constriction in Chinese subjects with angle closure
Authors: Zheng, C.
Cheung, C.Y.
Aung, T.
Narayanaswamy, A.
Ong, S.-H. 
Friedman, D.S.
Allen, J.C.
Baskaran, M.
Chew, P.T.
Perera, S.A.
Issue Date: Oct-2012
Citation: Zheng, C., Cheung, C.Y., Aung, T., Narayanaswamy, A., Ong, S.-H., Friedman, D.S., Allen, J.C., Baskaran, M., Chew, P.T., Perera, S.A. (2012-10). In vivo analysis of vectors involved in pupil constriction in Chinese subjects with angle closure. Investigative Ophthalmology and Visual Science 53 (11) : 6756-6762. ScholarBank@NUS Repository.
Abstract: PURPOSE: To evaluate the acceleration of pupil constriction (APC) in response to illumination using video anterior segment optical coherence tomography (AS-OCT) in angle closure and normal eyes. METHODS: This was an observational study of 342 Chinese subjects. Iris and angle changes in response to illumination were captured with real-time video recordings of AS-OCT and analyzed frame by frame. APC was calculated using a quadratic function, fitting pupil diameter to a time series. APC was divided into two vector components: acceleration of pupil block (APB) acting perpendicular to the lens surface and acceleration of iris stretch (AIS) acting toward the iris root. RESULTS: Of 342 eligible patients, 306 (89.5%) were available for analysis; of whom 136 (41.7%) had angle closure. After adjusting for age, sex, baseline pupil diameter, and iris thickness, APC was significantly lower in angle closure eyes (0.61 mm/s2) than in open-angle eyes (0.90 mm/s2) (P < 0.0001) as was AIS (0.58 mm/ s2 vs. 0.89 mm/s2) (P < 0.001). APB was significantly higher in angle closure eyes compared to open-angle eyes (0.14 mm/s2 vs. 0.09 mm/s2) (P < 0.001). After adjusting for age and sex in logistic regression, the magnitude and direction of all vector parameters were significantly associated with presence of angle closure. CONCLUSIONS: Angle closure eyes have smaller AIS and larger APB in response to illumination as measured using AS-OCT videography. This shows that, comparatively, the iris of angle closure eyes stretches less and develops a more convex configuration in response to illumination. © 2012 The Association for Research in Vision and Ophthalmology, Inc.
Source Title: Investigative Ophthalmology and Visual Science
ISSN: 01460404
DOI: 10.1167/iovs.12-10415
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