Association of anterior segment parameters and 5-year incident narrow angles: findings from an older Chinese population

Purpose To assess the association of anterior segment optical coherence tomography (AS-OCT) parameters and 5-year incident narrow angle in China. Methods This was a prospective cohort study of people aged 50 and older residing in Liwan District, Guangzhou, China. Random clustering sampling was used to identify adults aged 50 years and older in Liwan District, Guangzhou. In 2008 and 2013, this study was repeated and added AS-OCT imaging under dark and light conditions. Customised software (ZAAP) was used to analyse horizontal AS-OCT scans. Angle opening distance (AOD), trabecular iris space area (TISA), anterior chamber volume (ACV) and maximal iris thickness (ITM) were measured. Multiple logistic regression analysis models were used to investigate the associations of the final angle status with baseline AS-OCT parameters. ORs and 95% CIs were calculated. Results Of the 220 subjects with eligible AS-OCT images and gonioscopic results in 2008, the response rate was 77.3%. A total of 27 (15.9%) subjects developed narrow angles and 143 (84.1%) had open angles on gonioscopy in 2013. Subjects developed narrow angles had greater spherical equivalent and shallower anterior chamber depth, smaller angle parameters, thicker IT750 and ITM, smaller anterior chamber parameters, greater lens vault, and smaller dynamic parameters (Delta ITM, Delta ACA, Delta ACV) at baseline. After adjusting confounders, the predictors of incident narrow angles included smaller AOD750, TISA750, Delta ACA and greater ITM, Delta Iarea. Conclusions Incident narrow angles were associated with smaller anterior ocular dimensions, thicker iris and smaller light-to-dark changes at baseline. These findings can help in early diagnosis in this population.