Difference in the posterior pole profiles associated with the initial location of visual field defect in early-stage normal tension glaucoma

PurposeTo identify the differences in posterior pole profiles between early normal tension glaucoma (NTG) patients with an initial central visual field (VF) loss and those with a peripheral VF loss. MethodsNormal tension glaucoma patients with parafoveal scotoma (PFS; within a central 10 degrees of fixation; superior, n=47; inferior, n=24) and peripheral nasal step (PNS; VF defect in the nasal meridian outside 10 degrees of fixation; superior, n=27; inferior, n=32) in either hemifield were enrolled, if their mean deviation was greater than -10 decibels (dB). Disc tilt (tilt ratio), disc torsion, area of peripapillary atrophy and disc-foveal angle (angle between a horizontal line through the disc centre and the line connecting the fovea and the disc centre) were analysed from red-free fundus photographs. ResultsThe mean disc-foveal angles (shortest diameter) in PNS and PFS groups were 6.24.5 and 7.7 +/- 4.0 degrees, respectively. In multivariate analysis, eyes with PFS were associated with a greater disc-foveal angle, compared with PNS (p=0.042). In subgroup analysis, superior PFS group showed greater disc-foveal angle compared with inferior PFS group (p=0.018). In the PNS group, the direction of disc torsion was associated with superior and inferior hemifield defects (p=0.004). ConclusionsThe posterior pole profiles were different in NTG patients according to their location of damage. Disc-foveal angle was the major determinant of the VF location in patients with VF loss at the central region and disc torsion in patients with loss at the peripheral region.