Effect of Optic Disc Size on Retinal Nerve Fiber Layer Thickness and Peripapillary Vascular Density in Advanced...

In advanced primary open angle glaucoma, larger optic discs were associated with thicker retinal nerve fiber layers, while peripapillary vascular density remained unaffected by disc size, indicating structural but not microvascular dependence.

To evaluate the effect of optic disc size on peripapillary retinal nerve fiber layer thickness and peripapillary vascular density in patients with advanced primary open angle glaucoma.

This retrospective, observational study included 50 eyes from 50 patients with advanced primary open angle glaucoma and similar cup-to-disc ratios (0.7-0.8). Participants were divided into 2 groups according to optic disc area: <2.1 mm 2 (small-disc group, n=29) and ≥2.1 mm 2 (large-disc group, n=21). All subjects underwent spectral-domain optic coherence tomography angiography to measure retinal nerve fiber layer thickness and peripapillary vascular density. Structural and vascular parameters were compared between groups, and multiple linear regression analysis was performed to identify factors associated with retinal nerve fiber layer thickness and peripapillary vascular density.

Baseline demographic and ocular characteristics were comparable between groups. Eyes with larger optic discs exhibited significantly greater retinal nerve fiber layer thickness in the superior ( P =0.001), inferior ( P =0.001), and nasal ( P =0.032) quadrants, while temporal thickness and pVD showed no significant differences ( P >0.05). Multivariate regression revealed that optic disc area ( β =0.31, P <0.001), mean deviation ( β =0.35, P =0.010), and pattern deviation ( β =-0.26, P =0.038) were independent predictors of retinal nerve fiber layer thickness. In contrast, mean deviation ( β =0.36, P =0.039) and axial length ( β =-0.24, P =0.023) independently influenced peripapillary vascular density, while optic disc area did not.

Peripapillary vascular density appears to be less influenced by optic disc morphology compared with RNFL thickness and may serve as a complementary parameter, particularly in eyes with atypical optic disc anatomy.