OPTIC DISC SIZE AND OPTIC-NERVE DAMAGE IN NORMAL-PRESSURE GLAUCOMA

Background-Recent reports indicate that eyes with normal pressure glau coma have larger optic discs than eyes with primary open angle glaucom a or normal eyes. This study was performed to find whether, in normal pressure glaucoma, a large disc is associated with more optic nerve da mage than a small disc. Methods-Colour optic disc photographs of 74 pa tients with normal pressure glaucoma were assessed morphometrically. R esults-Taking the study group as a whole, the optic disc size decrease d significantly (p=0.04) with increasing visual field defect. In an in traindividual bilateral comparison, the side differences in the disc a rea of the right minus the left eye of the same individual were not si gnificantly correlated with the side differences in the mean visual fi eld defect. Conclusions-The results indicate that the eye with the lar ger optic disc, when compared with the contralateral eye with the smal ler optic nerve head, showed neither a significantly more marked nor l ess pronounced glaucomatous optic nerve damage. It suggests that for a given patient the degree of glaucomatous optic nerve atrophy was not markedly associated with the optic disc size. The finding that patient s with large visual field defects had smatter discs than patients with moderate perimetric loss may indicate that the results of previous cr oss sectional studies reporting on an unusually large disc size in nor mal pressure glaucoma may be due partially to selection.