To investigate whether there are differences in ocular risk factors reportedly associated with the development of normal tension glaucoma (NTG) between glaucomatous eyes and normal visual field (VF) eyes of monocular NTG patients.

Thirty-six patients who had NTG in one eye and normal RNFL and VF in the fellow eye were included in this hospital-based cross-sectional retrospective survey. We analyzed the difference between glaucomatous eyes and normal VF eyes according to an intra-individual, inter-ocular comparison of ocular parameters, including intraocular pressures (IOP), central corneal thickness (CCT), optic disc size, myopia, optic disc hemorrhage, and zone β of peripapillary atrophy. Measurements of optic disc size and area and the angular and radial extent of zone β were obtained using a Heidelberg Retina Tomograph. We also evaluated the correlation of each parameter with mean deviation (MD) and pattern standard deviation (PSD).

There were no inter-ocular differences of IOP, CCT, optic disc size, or myopia (n=36). Optic disc hemorrhage was found in only three glaucomatous eyes. The area of zone β was greater in glaucomatous eyes than in normal VF eyes (p=0.003). No parameters were correlated with MD or PSD.

Except for optic disc hemorrhage and zone β area, all other parameters showed no inter-ocular differences. The asymmetry of disc hemorrhage and zone βarea in monocular NTG patients implies that optic disc ischemia might play a role in the pathogenesis of NTG.