Optic disc morphometry in chronic primary open-angle glaucoma : I. Morphometric intrapapillary characteristics

A method is described which allows the real diameter of an object on the fundus to be determined by means of a system of curves which are the result of trigonometrical calculations and which give an approximate value; only a photograph of the fundus, a measurement of the ametropia and of the radius of the anterior surface of the cornea are required. The results can be corrected with a second graph, which makes use of the length of the optical axis of the eye.

The etiology of anterior ischemic optic neuropathy (AION), when not associated with giant cell arteritis, is usually unknown. Clinical, pathologic, and experimental studies have not determined a cause. The optic disc appearance in both the involved and normal fellow eye was studied in 51 patients with acute nonarteritic AION. The number of discs (both involved and fellow) without a physiologic cup was significantly greater than would be expected from normal population studies. The etiology of nonarteritic AION may be related to the anatomic configuration of the optic nerve.

From projected optic disk photographs we measured the size of the scleral canal in two samples of emmetropic patients: one of patients with unilateral pseudopapilledema and drusen and the other of the general normal population. Measurements on the non-drusen-containing optic disk of patients with unilateral drusen were taken to reflect the scleral canal size of the fellow, affected eye. For both trained (t = 6.642) and untrained (t = 4.274) observers, the average diameters of the non-drusen-containing optic disks of patients with unilateral drusen were significantly smaller than those of the optic disks of normal patients (P = .0005, one-tailed independent t-test). The association of a small scleral canal with vascular anomalies, frequently noted in optic disks of patients with drusen, indicates a mesodermal dysgenesis of the optic nerve head.