Relationship between central corneal thickness and optic nerve head parameters in primary open-angle glaucoma

Background: Primary open-angle glaucoma (POAG) is an ocular entity that causes optic neuropathy. Thin central corneal thickness (CCT) in patients with POAG correlates with changes in various optic nerve head structural parameters. Additionally, racial differences exist in CCT and optic disc parameters. Herein, we assessed the potential relationship between CCT and optic nerve head parameters in treatment-naive patients of Persian ethnicity who were diagnosed with POAG of varying severity levels. Methods: This hospital-based analytical cross-sectional study recruited patients of Persian ethnicity diagnosed with treatment-naive POAG. Participants underwent detailed optometric and ophthalmic examinations. Visual field testing was performed using a Humphrey perimeter. Spectral-domain optical coherence tomography (OCT) was performed using a Cirrus OCT device to record optic nerve head parameters: disc area, rim area, vertical cup-to-disc ratio, average cup-to-disc ratio, cup volume, and average retinal nerve fiber layer thickness (RNFLT). The CCT was measured using an ultrasonic pachymeter. Results: We recruited 168 eyes of 84 patients with POAG with a mean (standard deviation) age of 60.30 (12.50) years, comprising 33 (39.29%) men and 51 (60.71%) women. While weak but statistically significant inverse correlations of CCT with the vertical cup-to-disc ratio (r = - 0.19; P < 0.05), average cup-to-disc ratio (r = - 0.17; P < 0.05), and cup volume (r = - 0.17; P < 0.05) were found, other optic nerve parameters showed no significant correlations with CCT (all P > 0.05). Stepwise multiple linear regression analysis indicated that, for each unit increase in the vertical cup-to-disc ratio, the CCT decreased by 54.98 µm (P < 0.05). Conclusions: The CCT in eyes with treatment-naive POAG of varying severity levels in a Persian ethnic group was weakly but statistically significantly inversely correlated with the vertical cup-to-disc ratio, average cup-to-disc ratio, and cup volume. For every unit increase in the vertical cup-to-disc ratio, the CCT decreased by 54.98 µm. Our findings indicate that in patients with POAG, CCT correlates with some changes in structural optic nerve head parameters, including the cup volume and vertical/average cup-to-disc ratios. Further longitudinal studies including individuals from various racial backgrounds and POAG severity levels are needed to verify the relationship between CCT and optic nerve parameters at different time points of disease progression.