A simple clinical method of assessing patients with optic nerve hypoplasia. The disc-macula distance to disc diameter ratio (DM/DD).

The diagnosis of optic nerve hypoplasia may be difficult when the optic disc is only slightly reduced in size, or when central visual acuity is normal, or only minimally decreased. In these cases, measurement of the DM/DD ratio can provide a valuable tool in establishing the diagnosis. By means of fundus photographs the ratio of the distance between the centre of the optic disc and the fovea centralis, to the diameter of the optic disc (the DM/DD ratio) is measured. We have calculated the DM/DD ratio in 19 eyes of 11 patients with optic nerve hypoplasia and found it to be significantly higher than the ratios obtained for 58 eyes of 48 normal subjects, 22 eyes of 11 patients with primary open angle glaucoma and 25 eyes of 16 patients with optic atrophy. The DM/DD ratio is easily estimated and is recommended as a simple means of establishing the diagnosis of optic nerve hypoplasia.