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B. Wang, L. M. Sakata, Y. H. Chan, M. He, R. Lavanya, D. S. Friedman, T. Y. Wong, T. Aung; Increased Iris Thickness and Curvature Are Risk Factors for Angle Closure. Invest. Ophthalmol. Vis. Sci. 2009;50(13):3358.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the relationship between iris parameters and risk of angle closure (AC).
This cross-sectional observational study included 2047 subjects over 50 years old recruited from a community clinic in Singapore. All subjects underwent gonioscopy and AS-OCT imaging under identical standardized conditions. Gonioscopy was performed by a single masked examiner in the dark, and AC was defined as the presence of at least 180 degrees of angle in which the posterior pigmented trabecular meshwork was not visible on non-indentation gonioscopy in the primary position. AS-OCT imaging in the dark was performed by a single masked operator using the commercially available Visante-OCT (Carl-Zeiss Meditec, Dublin/USA). Customized software was used on horizontal ASOCT scans to measure the following iris parameters: iris thickness 750um (IT750) and 2000 um (IT2000) from the sclera spur, iris curvature (I-Curv) and cross-sectional area of the iris (I-Area). The right eye of all subjects and an average of both temporal and nasal measured values were used for analysis.
Participants were excluded mainly due to poor AS-OCT image quality or poor definition of the scleral spur. Iris parameters from 1465 eyes were available for analysis. Of these, 315 subjects (21.5%) had AC on gonioscopy. Mean I-Curv (0.366mm v 0.259mm, p<0.001), IT750 (0.476mm v 0.453, p<0.001) and IT2000 (0.491mm v 0.482mm, p=0.020) were greater in those with than without AC. After adjusting for age, gender, body-mass index, anterior chamber depth and axial length, greater I-Curv, IT750 and IT2000 remained significantly associated with AC (4th vs 1st quartile, multivariate adjusted OR 2.5, 95%CI 1.3-5.1; OR 3.0, 95% CI 1.9-4.7 ; OR 3.7, 95% CI 2.2-6.3 respectively) while I-Area was not significant (OR 1.3, 95% CI 0.8-2.1).
Our findings show that iris curvature and thickness are risk factors for angle closure even after adjusting for other known ocular risk factors.
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