Influence of Refractive Error on Circumpapillary Structure–Function Versus Vessel Density–Function Relationships in Open Angle Glaucoma

Abstract

Précis: In Japanese open angle glaucoma (OAG) eyes correlation of 30-degree visual field mean deviation (MD) and visual field index (VFI) with circumpapillary vessel density is systematically stronger than that with circumpapillary retinal nerve fiber layer thickness (RNFLT), and is preserved in myopia and high myopia. Purpose: The purpose of this study was to investigate the influence of refractive error on the relationship between circumpapillary retinal nerve fiber layer thickness (cpRNFLT) and circumpapillary vessel density (cpVD), respectively, and global visual field parameters in Japanese open angle glaucoma (OAG) eyes. Material and Methods: One eye of 81 Japanese OAG patients (spherical equivalent refractive error: +3.0 to −9.0 D) underwent 360-degree cpRNFLT and cpVD measurements with Cirrus HD 5000-AngioPlex optical coherence tomography and 30-2 Humphrey visual field testing for mean deviation (MD) and visual field index (VFI) within 1 month. Correlations were determined for the whole population and each refractive error subgroups, separately: emmetropia/hyperopia (n=24), mild (n=18), moderate (n=20), and high myopia (n=19). Results: For the total population, significant strong to very strong correlations were found between MD, VFI, and both cpRNFLT and cpVD, respectively, with consistently higher r-values for cpVD (highest r-values: 0.532 for cpRNFLT, P<0.001; 0.722 for cpVD, P<0.001). Of the refractive subgroups, statistically significant correlations between cpRNFLT and the visual field parameters were maintained only in the hyperopia/emmetropia and moderate myopia groups. In contrast, statistically significant, strong to very strong correlations between cpVD and both MD and VFI, always exceeding the corresponding r-values found for cpRNFLT were found in all refractive subgroups, with r-values ranging between 0.548 (P=0.005) and 0.841 (P<0.001). Conclusions: Our results suggest that in Japanese OAG eyes the relationship of MD and VFI with cpVD is strong. It is systematically stronger than that with cpRNFLT and preserved in each conventional refractive error category including high myopia.