To evaluate ocular risk factors related to asymmetric visual field defects in normal tension glaucoma (NTG).

We retrospectively evaluated 92 NTG patients (184 eyes) with asymmetric visual field defects; these patients were classified as having more affected eye (ME) group or less affected eye (LE) group. The differences between ME and LE based on the intra-individual comparison were assessed with several ocular risk factors such as best corrected visual acuity, refractive error, intraocular pressure (IOP), the number of glaucoma medications, disc hemorrhage, central corneal thickness, zone β of peripapillary atrophy (PPA), and disc size. All subjects were divided into two groups according to the severity of bilateral mean deviation (MD, Δ6dB) and evaluated.

The MD was -11.2±6.5 in the ME group, and -5.9±5.4 in the LE group ( p =0.00). The optic disc size was 2.62±0.8 in the ME group, 2.48±0.5 in the LE group ( p =0.00), and there were no statistically significant differences in the other factors. Regarding the difference in the MD, the optic disc size was statistically significant in the less different group, and the angle of PPA was statistically significant in the more different group ( p =0.00 and p =0.01, respectively).

The optic disc size is a risk factor related to visual field defects in the ME group and the less affected patients, and the PPA is a risk factor, thought to be associated with ischemia, related to visual field defects in the more affected patients with asymmetric normal tension glaucoma.