Investigation of optic nerve head microvascular changes in primary open angle glaucoma and chronic angle closure glaucoma using OCT-angiography

Abstract

Purpose : To identify optic nerve head (ONH) microvascular abnormalities by OCT-angiography (OCT-A) in patients with primary open angle glaucoma (POAG) or chronic angle closure glaucoma (CACG), compared to controls without significant ocular pathology. Previous studies have reported reductions in the flow index and vascular density within the optic nerve head of patients with POAG. However, it is not known whether similar changes are present in patients with CACG.

Methods : Patients with POAG or CACG and reproducible VF loss, as well as control subjects, were recruited for a prospective, cross-sectional study. One eye per subject was included. Angiograms were generated from swept source OCT (Topcon) covering a 3x3mm region centered on the ONH, based on a previously described SSDA algorithm. Blood vessels were quantified by generating en face images from the internal limiting membrane (ILM) to a depth of 130µm (superficial vasculature) or from 130-390µm below the ILM (deep vasculature). The ONH area for quantification was defined based on Bruch’s membrane opening.

Results : Preliminary data are presented for 5 control, 5 POAG and 4 CACG patients. All groups were similar in age (mean age 69.7±2.5 overall; Table 1A). Patients with POAG and CACG had similar Humphrey Visual Field mean deviations (mean -5.21 ± 1.73dB overall). The superficial ONH flow index was reduced by 16% in POAG patients in comparison to control patients (p=0.008), and vascular density was reduced by 7.8% (p=0.04), consistent with previously published studies (Figure 1; Table 1B-C). In contrast, there was no significant reduction in either ONH flow index or vascular density in CACG patients relative to control patients, and measurements for these two groups were within 2% of each other. The comparison between POAG and CACG groups showed reduced superficial ONH flow index (p=0.03) and vascular density (p=0.05) in POAG patients. Notably, no significant differences in the deep ONH vasculature were identified across the three groups.

Conclusions : Our preliminary results suggest that POAG might be associated with more pathology of the ONH microvasculature than CACG. These differences highlight that distinct pathophysiologic processes underlie damage to the optic nerve in POAG and CACG. Further enrollment is ongoing to verify these findings.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.