The neuroretinal rim area reflects the amount of optic nerve fibers, while it is also related to the size of the optic disc. Minima of normal rim area at the 95% confidence level in relation to disc area in 172 normal eyes were established, and 81 eyes of early open angle glaucoma and 81 eyes of suspected glaucoma were assessed with these criteria in comparison with assessments according to the rim area alone without consideration of the size of the optic disc. The results in the glaucoma group indicated that the positive rate by the present method was 72.8% in contrast to 45.7% by the rim area alone, the difference being very significant (P less than 0.01). However, the new method was less sensitive to glaucoma patients with large optic discs.