Optic Nerve Head Characterization in Chronic Angle Closure Glaucoma Detected by Swept-Source OCT

Abstract

Purpose : To identify differences in optic nerve head (ONH) structures in chronic angle closure glaucoma (CACG) compared to primary open angle glaucoma (POAG) and controls using swept-source optical coherence tomography (SS-OCT).

Methods : Patients with CACG, age-matched POAG patients and healthy control subjects underwent radial and volume B-scans of the ONH by SS-OCT. Minimum rim width at Bruch’s membrane opening (BMO-MRW), horizontal and vertical lamina cribrosa depth (LCD) were measured using customized ImageJ plugins. Prelaminar defects, categorized as hole and wedge (Figure), and lamina cribrosa (LC) defects were identified. One eye per subject was analyzed. The difference of quantity measurements among the three groups were compared using Analysis of Variance (ANOVA). The detection rates of defects from each group were compared by Fisher’s exact test.

Results : 72 subjects (12 CACG, 40 POAG and 20 controls) were included. CACG and POAG groups were similar in mean deviation on Humphrey visual field (-6.67±3.95 vs -6.25±5.96 dB) and IOP on the day of imaging (13.8± 3.0 vs 13.9±2.6 mmHg), although maximum IOP was higher in CACG (28.2±15.7mmHg) than POAG group (20.7±4.5mmHg, p=0.006) (Table). Thinner BMO-MRW was found in CACG (122.8±45.2μm, p<0.001) and POAG (102.1±65.8μm, p<0.001) groups compared to controls (221.6±38.2μm). However, no significant difference in horizontal and vertical LCD was found among the groups. At least one prelaminar hole (Figure) was found in 66.7% of CACG eyes compared to 25.0% in POAG (p=0.001) and 25.0% in control eyes (p=0.011). No prelaminar wedge defect or LC defect was present in the CACG group, but both types of defects were found in POAG group (Table).

Conclusions : While SS-OCT evaluation of the ONH revealed thinner BMO-MRW in both CACG and POAG groups compared to controls, prelaminar holes were most frequent in CACG patients suggesting this may be a distinguishing feature of CACG.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.

 

Figure. SS-OCT Images of ONH Prelaminar Defects. Multiple large holes in CACG (A); one small hole in POAG (B); wedge defect extending to LC in POAG (C).