Influence of optic disc appearance and diurnal variation of intraocular pressure on visual field defect in normal tension glaucoma

One hundred and eleven stereo optic disc photographs of patients with normal tension glaucoma (NTG) were reviewed in order to identify the characteristics of four types of NTG: focal ischemic (FINTG), generalized cup enlargement (GENTG), myopic (MYNTG), and senile sclerotic (SSNTG). Twenty-five patients with FINTG, 45 with GENTG, 28 with MYNTG, and 14 with SSNTG were identified. The four groups showed significant differences in the presence of localized or diffuse visual field defects (p = 0.008). Patients with FINTG and MYNTG had localized visual field defects only. Conversely, in half of the patients with GENTG and SSNTG, diffuse and localized loss were both present. There was a significant difference in the pattern of diurnal intraocular pressure (IOP) variation among the four groups (p = 0.002). Patients with MYNTG showed a flat type of diurnal IOP variation more frequently than those in the other three groups. These results suggested that NTG has pathogenic mechanisms which differ according to the optic disc type and degree of IOP variation.