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

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.