Comparative evaluation of anterior segment parameters in subgroups of primary angle closure using anterior segment optical coherence tomography

Abstract

Purpose: Anterior segment optical coherence tomography (ASOCT) allows measurement of anterior segment parameters associated with angle closure. The aim of this study was to compare these parameters in subjects categorized as primary angle closure suspect (PACS), primary angle closure (PAC), primary angle closure glaucoma (PACG), and previous acute primary angle closure (APAC).

Methods: This was a prospective observational study of 425 subjects with angle closure, consisting of 176 PACS, 66 PAC, 125 PACG and 58 APAC subjects. Each subject underwent a standardized eye examination and ASOCT imaging. Customized software (Zhongshan Angle Assessment Program, Guangzhou, China) was used to measure ASOCT parameters, including angle opening distance (AOD), trabecular-iris space area (TISA), angle recess area (ARA), anterior chamber depth (ACD), anterior chamber width (ACW), anterior chamber area (ACA), and anterior chamber volume (ACV), iris thickness (IT), and lens vault (LV). One-way analysis of variance (ANOVA) with Bonferroni adjustments was used to evaluate the mean differences between subgroups. Logistic regression analysis was performed to identify determinants for APAC.

Results: Comparison among the different subgroups showed that ACD, ACA and ACV were significantly smallest, and the iris thickest (IT750) in the APAC group compared to the other subgroups (ANOVA p<0.001 for all). The LV was greatest in the APAC group (1194±289µ) followed by PACG (876±270µ), PAC (865±240µ) and PACS (789±253µ), respectively (ANOVA p=<0.001). While the APAC group had the narrowest angles, the PACS group had the widest (AOD750: 0.12±0.07 vs. 0.27±0.10, respectively, p<0.001 and TISA750: 0.07±0.03 vs. 0.15±0.05, respectively, p<0.001). A multivariate adjusted logistic regression showed that a greater LV (p=<0.001), narrower TISA (p=<0.001) and a thicker iris (p=0.014) were the major determinants of APAC.

Conclusions: Eyes with APAC had the narrowest angles, smallest anterior segment dimensions, thickest iris and largest LV compared with PACS, PAC and PACG. The LV, TISA750 and IT750 were the major determinants of APAC.

Keywords: 421 anterior segment • 550 imaging/image analysis: clinical