Examining systemic microvascular abnormalities in primary open-angle glaucoma using nailfold videomicroscopy

Abstract

Purpose: Primary open-angle glaucoma (POAG) continues to be a disease of unknown etiology. While disc hemorrhages are known to occur with disease progression, the question remains whether there are also vascular abnormalities in non-ocular capillary beds. The purpose of this study is to examine nailfold capillary structure and determine if systemic vasculature abnormalities exist in POAG patients.

Methods: Nailfold videomicroscopy control subjects were analyzed on 160 POAG and 170 control subjects who were between the ages of 40-80 at 4 clinical centers. All controls had IOP< 21 mm Hg OU and cup-disc ratio of 0.6 or less, OU. All POAG patients cases had manifest visual field loss on reliable standard automated perimetric tests. Masked observers graded nailfold capillary videos for the presence of hemorrhages, dilated capillary loops (>50μm), and avascular areas >200μm. Intraobserver and interobserver agreement for these exposures were high. Chi Square and unpaired t-tests were used for statistical analysis.

Results: The mean age of cases and controls was comparable (65.1±9.2 vs. 63.4±9.5 years). Video documented nailfold micro-hemorrhages were present in 82.5% of POAG patients compared to 34.7% of controls (p=0.0001). The mean number of micro-hemorrhages per 100 capillaries in POAG was 1.96±2.7 compared to 0.78 ±1.7 in controls (p=1.67x10^-6). Dilated capillaries were present in 48.1% of POAG patients and 34.7% of control subjects (p=0.87). Avascular zones were observed in 12.6% POAG vs. 3.6% controls. The number of avascular zones per 100 capillaries in POAG was 0.12±0.3 compared to the control 0.03±0.17 (p=0.002).

Conclusions: POAG patients had more nailfold hemorrhages and more avascular zones compared to controls, supporting the notion that non-ocular microvascular abnormalities exist in these patients. The etiology of these peripheral microvascular findings requires further evaluation.