Effect of Angle Narrowing on Sectoral Variation of Anterior Chamber Angle Width The Chinese American Eye Study

Purpose: To characterize the relationship between mean and sectoral variation of anterior chamber angle (ACA) width using anterior segment (AS)-OCT. Design: Cross-sectional study with sectoral variation of anterior chamber angle width as the main outcome measure. Participants: Participants 50 years of age or older were identified from the Chinese American Eye Study (CHES), a population-based epidemiologic study in Los Angeles, California. Methods: Participants underwent a complete ocular examination including gonioscopy and AS-OCT imaging. Primary angle-closure disease (PACD) was defined as inability to visualize pigmented trabecular meshwork in 3 or more quadrants. Four AS-OCT images from 1 eye per participant were analyzed, and parameters describing ACA width were measured at 500 and 750 mu m from the scleral spur: angle opening distance (AOD(500) and AOD(750)), trabecular iris space area (TISA(500) and TISA(750)), and scleral spur angle (SSA(500) and SSA(750)). The relationship between mean and sectoral variation of ACA width was assessed using locally weighted scatterplot smoothing (LOWESS) regression, change-point analyses, and Spearman correlation coefficients. Results: Six hundred seventy-four eyes (337 with PACD, 337 without PACD) from 674 participants were analyzed. Overall, sectoral variation of ACA width decreased as mean ACA width decreased. This relationship was divided into 2 phases based on the change-point analysis. Sectoral variation of ACA width was correlated strongly and significantly (P < 0.001) with mean ACA width with below parameter-specific change points for most parameters: AOD(500) (r = 0.599), AOD(750) (r = 0.246), TISA(500) (r = 0.734), TISA(750) (r = 0.664), SSA(500) (r = 0.661), and SSA(750) (r = 0.394). Correlations were weaker but still significant (P < 0.004) above these change points for most parameters: AOD(500) (r = 0.321), AOD(750) (r = 0.550), TISA(500) (r = 0.122), TISA(750) (r = 0.275), SSA(500) (r = -0.036), and SSA(750) (r = 0.313). Correlations to the left and right of the change points strengthened when sectoral variation of ACA width was adjusted for mean ACA width. Conclusions: Correlations between mean and sectoral variation of ACA width strengthen as the severity of angle narrowing worsens. This relationship likely reflects anatomic changes related to chronic angle closure and may be relevant for refining current definitions and management of PACD. (C) 2019 by the American Academy of Ophthalmology