KHẢO SÁT MẬT ĐỘ MẠCH MÁU QUANH GAI THỊ TRÊN GLAUCOMA GÓC MỞ NGUYÊN PHÁT GIAI ĐOẠN SỚM BẰNG MÁY CHỤP CẮT LỚP QUANG HỌC MẠCH MÁU

Abstract

Background: Glaucoma is a chronic optic neuropathy and the second leading cause of blindness worldwide, characterized by progressive degeneration and apoptosis of retinal ganglion cells (RGCs). The exact pathophysiological mechanism of glaucoma remains unclear. Prospective studies on primary open-angle glaucoma (POAG) have shown a reduction in retinal and choroidal blood flow, leading to vascular dysregulation at the optic nerve head (ONH) and subsequent retinal ganglion cell damage. Optical coherence tomography angiography (OCT-A) is a highly precise and non-invasive imaging technique that allows the evaluation of the optic disc and retinal microvasculature by detecting erythrocyte movement through high-resolution cross-sectional scans. This method indirectly provides insights into vessel density and blood flow velocity in the peripapillary region. Objective: To evaluate peripapillary vessel density on OCT-A in early-stage primary open-angle glaucoma. Methods: A cross-sectional, analytical descriptive study was conducted on 93 eyes from 88 patients diagnosed with early-stage primary open-angle glaucoma. These patients presented to the Ho Chi Minh City Eye Hospital and underwent comprehensive ophthalmic examinations, including OCT, OCT-A, and visual field (VF) testing, between November 2019 and July 2020. Results: The study found a higher proportion of male patients (65.5%) compared to female patients (61.9%). The mean age in the early-stage glaucoma group (Group 1) was 60.3±7.8 years (range: 41–72 years); in the pre-perimetric glaucoma group (Group 2), it was 60.3±6.3 years (range: 50–71 years); and in the control group (Group 3), it was 57.9±6.7 years (range: 43–69 years). Mean intraocular pressure (IOP) across all three groups ranged from 16.0±4.7 mmHg to 18.6±4.3 mmHg, with no significant difference between groups. The study also revealed that the average retinal nerve fiber layer (RNFL) thickness in the pre-perimetric glaucoma group was greater than in the early-stage glaucoma group. In pre-perimetric glaucoma cases, despite no detectable functional impairment, structural changes in ganglion cells were already evident. The mean ganglion cell complex (GCC) thickness values in Groups 1, 2, and 3 were 75.48±9.3 µm, 77.33±11.38 µm, and 83.98±11.68 µm, respectively. A statistically significant progressive decline was observed in visual field indices (MD and PSD) across the three groups. In patients with perimetric glaucoma, a statistically significant positive correlation was demonstrated between peripapillary capillary perfusion density (P) and flow index (F) with RNFL thickness (p<0.05). Furthermore, a strong positive correlation was found between vascular indices (P and F) and the mean deviation (MD) of visual field testing, with correlation coefficients (r) of 0.67 and 0.61, respectively. A moderate correlation was also observed between these vascular indices and PSD (r = 0.38 and 0.36). Regarding the diagnostic ability of OCT-A parameters, the perfusion density index (P) demonstrated good discrimination between the early-stage glaucoma (Group 1) and pre-perimetric glaucoma (Group 2) compared to the control group, with area under the curve (AUC) values of 0.824 and 0.835, respectively. Conversely, the AUC value for the flow index (F) when differentiating pre-perimetric glaucoma (Group 2) from the control group was only 0.668, indicating that F is a poor or unreliable parameter for diagnosing pre-perimetric glaucoma. Conclusion: OCT-A serves as a valuable adjunct tool alongside RNFL thickness, ganglion cell complex measurements, and visual field assessment in diagnosing and monitoring primary open-angle glaucoma, particularly in the early stages and in suspected glaucoma cases.