Comparative Analysis of Optical Coherence Tomography Angiography Metrics in Primary Open- Angle Glaucoma and Ocular Hypertension

Purpose: To investigate the diagnostic and follow-up utility of optical coherence tomography angiography (OCT-A) in glaucoma by evaluating macular ganglion cell complex (GCC) thickness and parafoveal vessel density (pfVD) in patients with ocular hypertension (OHT) and various stages of primary open-angle glaucoma (POAG). Material and Methods: This cross-sectional study included 150 eyes from 56 patients with POAG and 32 with OHT, all under regular follow-up at the Glaucoma Unit of the Istanbul Faculty of Medicine, Department of Ophthalmology. Evaluations were conducted between November and December 2022.Additionally,50 eyes from 25 healthy individuals without ocular or systemic pathology were included as a control group. OCT-A images were obtained using the Topcon DRI OCT Triton (Topcon Corporation, Japan). Macular GCC thickness and pfVD in the superficial and deep capillary plexuses were measured and compared among the groups. Results: A total of 113 participants (74 females,39 males) were enrolled. No statistically significant differences in macular GCC thickness or pfVD were found between the control and OHT groups. In contrast, both parameters were significantly reduced in the POAG group, with a progressive decline corresponding to disease severity. The decrease in pfVD was more pronounced in the superficial plexus compared to the deep plexus. In early-stage POAG, GCC thinning was more prominent than pfVD reduction. Conclusıon: Our findings suggest that assessment of macular GCC thickness and pfVD via OCT-A can be utilized alongside structural and functional tests in the diagnosis and follow-up of glaucoma. In our study, macular GCC measurements were significantly lower in the glaucoma group compared to other groups, with more pronounced thinning observed in advanced stages. Notably, in early-stage glaucoma, the reduction in macular GCC was more prominent than that in pfVD. These findings indicate that structural damage in macular GCC may occur earlier than vascular changes in pfVD and may be particularly useful in the early monitoring of glaucoma progression.