Microvascular changes in the superficial peripapillary tissues during an induced acute elevation of the intraocular pressure in glaucoma.

Abstract

Purpose : The superficial vessel density (VD) analyzed by the optical coherence tomographic angiography (OCT-A) has presented good correlations with functional damage in glaucoma. Since it is unknown the immediate effects of an acute intraocular pressure (IOP) elevation on the peripapillary microvascular, we compared the superficial peripapillary VD before and during an induced, acute IOP elevation caused by an external compression to the eyes of patients with primary open-angle glaucoma (POAG) and healthy controls.

Methods : This cross-sectional study evaluated 15 eyes of seven PAOG patients and eight controls that underwent a periocular compression caused by the use of a drilled swimming goggles (SG). Goldman applanation tonometry and measurements of peripapillary VD were taken before (M0) and during a 5-minutes (M1) use of the SG. Good quality OCT-A en face images of the nerve fiber layer vascular plexus (NFLVP) and the superficial vascular plexus (SVP), combined or not in the superficial vascular complex (SVC), were acquired. The OCT-A images were processed, excluding vessels thicker than 40 um, and an imaging contrast metric based on the histogram spread of contrast from individual angiograms was applied. Higher image contrast between perfused and nonperfused capillaries' regions served as a surrogate metric for measuring VD changes between M0 and M1.

Results : SG significantly increased IOP (M0: 13.6 ± 3.2 mmHg vs. M1: 25.9 ± 9.1 mmHg, p = 0.001) and decrease VD of all layers (M0: 0.39 ± 0.10 contrast units vs. M1: 0.31 ± 0.10 contrast units, p < 0.0001 -Wilcoxon matched-pairs signed-rank test). A significant inverse correlation between IOP increase and VD was observed only in the SVP (Spearman r = - 0.62; p = 0.013), but no significant difference in the VD changes of any of the plexuses was observed between POAG patients and controls.

Conclusions : The provoked acute IOP elevation observed in this SG-wearing experiment induced an IOP-dependent VD decrease in the OCT-A acquired peripapillary SVP. Although no difference in the VD change was observed between POAG patients and controls in our sample, this model of transient global microvascular reduction strengthens the concept of the IOP-induced ischemic peripapillary damage in glaucoma.

This is a 2020 ARVO Annual Meeting abstract.