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Abstract #51183 Published in IGR 14-3
In vivo analysis of vectors involved in pupil constriction in Chinese subjects with angle closure
Zheng C; Cheung CY; Aung T; Narayanaswamy A; Ong SH; Friedman DS; Allen JC; Baskaran M; Chew PT; Perera SAInvestigative Ophthalmology and Visual Science 2012; 53: 6756-6762
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/s(2)) than in open-angle eyes (0.90 mm/s(2)) (P < 0.0001) as was AIS (0.58 mm/s(2) vs. 0.89 mm/s(2)) (P < 0.001). APB was significantly higher in angle closure eyes compared to open-angle eyes (0.14 mm/s(2) vs. 0.09 mm/s(2)) (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.
Singapore Eye Research Institute at the Singapore National Eye Centre, Singapore, Republic of Singapore.
Full articleClassification:
9.3.5 Primary angle closure (Part of: 9 Clinical forms of glaucomas > 9.3 Primary angle closure glaucomas)
2.8 Iris (Part of: 2 Anatomical structures in glaucoma)
6.30 Other (Part of: 6 Clinical examination methods)
