Comparative optic disc analysis in normal pressure glaucoma, primary open angle glaucoma and ocular hypertension

Purpose. We wished to determine whether parapapillary chorioretinal atrophy (PPA) and other characteristics of the optic nerve head differ between eyes with normal pressure glaucoma (NPG), primary open angle glaucoma (POAG) and ocular hypertension (OHT). In addition, we examined the optic disc parameters in a subset of NPG patients with evidence of serum abnormalities of humoral autoimmunity. Methods. 135 eyes of 68 NPG patients, 394 eyes of 197 POAG patients and 392 eyes of 196 OHT patients were analyzed. Nerve fiber layer hemorrhage (NFLH), retinal arteriolar narrowing and morphometric optic disc parameters such as ratios of neuro-retinal rim (NRR) to disc area, PPA to disc area and PPA length to the circumference of the disc were investigated in these groups. Results. NFLH and arteriolar narrowing were found more frequently (p<.001) in glaucoma patients than in patients with OHT and the statistical significance was higher in NPG than POAG. PPA occured more frequently in NPG (p<.001) and POAG (p<.001) than OHT and was seen frequently as zone alpha in OHT and zone beta was found frequently in NPG. There was a negative correlation between NRR area and the area and extension of PPA in NPG and POAG. Optic disc characteristics were not different (p>.05) between the subgroups of NPG. Conclusions. The absence of morphometric differences in optic disc parameters between NPG and POAG and between the subgroups of NPG suggests that the final clinical apperance of optic nerve damage is similar, regardless of their possibly different mechanisms of neuropathy. The increased frequency of zone beta of PPA that occurs in NPG and POAG likely reflects a common feature of PPA that accompanies advanced optic neuropathy in these patients.