Four hundred twenty-seven optic discs of 233 unselected patients suffering from chronic primary open-angle glaucoma were morphometrically evaluated and compared with the optic nerve heads of 253 unselected normal subjects. Only one randomly chosen eye per patient was taken into consideration. We found that glaucoma leads to a change in the characteristic configuration of the neuroretinal rim that in normal eyes is significantly (P less than 0.001) largest at the lower disc pole, smaller at the upper and nasal disc side, and smallest in the temporal disc region. Based on this information, significant (P less than 0.001) morphometric differences between "early" glaucomatous and normal discs are: (a) the neuroretinal rim area in the lower temporal disc sector is smaller than in the upper temporal disc sector; the smallest rim width is outside the horizontal temporal disc sector ("pathognomonic"); the quotient of horizontal to vertical c/d ratio is lowered; and (d) the lower temporal, upper temporal, and total rim area are decreased. No significant difference in overall optic disc size and form exists between normal and glaucomatous eyes. Smaller optic nerve heads are not more susceptible to glaucoma.