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

PURPOSE

To 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.

METHODS

Normal tension glaucoma patients with parafoveal scotoma (PFS; within a central 10° of fixation; superior, n=47; inferior, n=24) and peripheral nasal step (PNS; VF defect in the nasal meridian outside 10° 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.

RESULTS

The mean disc-foveal angles (shortest diameter) in PNS and PFS groups were 6.2±4.5 and 7.7±4.0°, 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).

CONCLUSIONS

The 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.