# Effects of Glaucoma Stage on Optical Coherence Tomography Angiography Parameters in Patients With Primary Open-Angle Glaucoma

## TL;DR

This study examines how glaucoma stages affect blood vessel patterns in the eye using OCTA, finding that early-stage glaucoma can be detected with specific vessel density measurements.

## Contribution

The study introduces new insights into OCTA parameters for detecting and staging primary open-angle glaucoma.

## Key findings

- OCTA radial peripapillary capillary vessel density has high diagnostic accuracy for early glaucoma detection.
- Macular vascular density is significantly reduced in moderate and advanced glaucoma stages compared to healthy eyes.
- Advanced-stage glaucoma shows more severe macular vascular damage than early-stage glaucoma.

## Abstract

Purpose

The purpose of this study is to evaluate the findings of optical coherence tomography angiography (OCTA) in patients with primary open-angle glaucoma (POAG) and investigate diagnostic power and correlations between the control group and patients at different stages of glaucoma.

Methods

This retrospective cross-sectional study included POAG patients and healthy volunteers as a control group. All subjects underwent a complete ophthalmological examination and computerised perimetry (GPc; Octopus 900, Haag-Streit AG, Köniz, Switzerland). Structural characteristics in the macular and peripapillary regions were assessed utilising optical coherence tomography (OCT; Cirrus HD-OCT 5000, Carl Zeiss Meditec, Dublin, CA, USA), and vascular parameters were assessed with OCTA (Optovue, RTVue XR100-2, Optovue Inc., Fremont, CA, USA). Additionally, the relationship between the glaucoma stage and OCTA findings was analyzed in patients and classified based on the global perimetry mean deviation value.

Results

The mean age of the POAG group (27 patients, 51 eyes) was 54.5±11.9 years, while the mean age was 45.1±9.7 years in the control group (54 patients, 54 eyes) (p=0.008). In terms of demographic features, the two groups did not differ significantly (p>0.05). The severity of the glaucoma was determined to be as follows: 24 eyes (47% of the total) were classified as early-stage, 12 eyes (23.5%) as moderate-stage, and 15 eyes (29.5%) as advanced-stage. OCTA radial peripapillary capillary (RPC) vessel density analyses showed that the inferior hemi's peripapillary vessel density (ppVD) area's under the receiver operating characteristic curve (AUC) (0.796 (0.665-0.927)) and the average ppVD (0.790 (0.658-0.921)) parameters had the best AUCs for early glaucoma detection. In the analysis of superficial macular vessel (SMV) density, all image upper-half (AI-UH), parafoveal upper-half (paf-UH), temporal (paf-T), superior (paf-S), and nasal (paf-N), as well as perifoveal upper-half (pef-UH), temporal (pef-T), and superior (pef-S) vessel densities were lower in moderate- and advanced-stage POAG eyes compared to healthy eyes (all p<0.05). Additionally, when glaucoma patients were analyzed together, SMV density measurements showed that AI, AI-UH, paf-UH, paf-T, paf-S, paf-N, pef, pef-UH, pef-T, and pef-N vessel densities were lower in advanced-stage POAG eyes compared to early-stage eyes (all p<0.05).

Conclusion

OCTA detected vascular damage in the macular and peripapillary regions in POAG patients. We found that ppVD helps identify early-stage glaucoma in RPC vessel density analysis. Moreover, macular vascular damage was observed to be more severe in advanced-stage glaucoma compared to early-stage glaucoma.