Relationship between disc margin to fovea distance and central visual field defect in normal tension glaucoma

Background To investigate the relationship between ocular geometric factors, including temporal disc margin to fovea distance (DFD) measured by optic disc stereophotography (ODP) and central visual field (VF) defect, in normal-tension glaucoma (NTG) patients. This retrospective, single-center, cross-sectional study included 88 eyes of 88 NTG patients with mild VF defects (MD > -6.0 dB). NTG patients were divided into two groups according to VF tests: central VF-invading and central VF-sparing groups. Optic nerve head (ONH) parameters including disc dimensions, peripapillary atrophy (PPA), and DFD were obtained by ODP, and retinal nerve fiber layer (RNFL) thickness was measured by Stratus optical coherence tomography (OCT). In the invading group, DFD was shorter (3.642 +/- 0.401 mm) than in the sparing group (3.877 +/- 0.278 mm; p = 0.002). The sparing group had more vertically oval ONH (p = 0.023) and wider temporal PPA width (p = 0.031). The RNFL thickness in the invading group was thinner in the temporal and inferior quadrants, but thicker in the superior quadrant than that of the sparing group. In a multiple linear regression analysis, DFD was the only geometric factor associated with degree of central VF involvement (p = 0.002). DFD was positively correlated with temporal RNFL thickness in the sparing group (r = 0.484, p < 0.001) but not in the invading group (r = -0.080, p = 0.631). Eyes with a shorter DFD should be monitored carefully because central VF involvement appears to be related to shorter DFD in NTG patients with mild VF defects.