Anterior ischemic optic neuropathy: a comparison of the optic disc area of patients with the arteritic and non-arteritic forms of the disease and that of normal controls.

PURPOSE To evaluate the optic disc area of patients with non-arteritic anterior ischemic optic neuropathy (NA-AION) and arteritic anterior ischemic optic neuropathy (A-AION) and compare the results between each other and with those from controls in order to verify the existence and the magnitude of anatomical factors predisposing to the development of anterior ischemic optic neuropathy. METHODS This is a case-controlled study of the optic disc area of 24 consecutive patients affected with NA-AION, 13 patients with A-AION and 24 consecutive healthy normals, sex- and age-matched with the patients with the NA-AION group. Measurements of optic disc area were performed for each studied group using disc photographs projected, measured and corrected for the refractive error and the keratometric readings, according to Littmann's method in each studied group. The results were compared using variance analysis. RESULTS The mean areas and standard deviations of the optic discs from patients with NA-AION, A-AION and normals were respectively 1.99 +/- 0.35 mm(2), 2.29 +/- 0.39 mm(2) and 2.49 +/- 0.53 mm(2). The statistical analysis revealed that the mean areas of the optic disc of patients with NA-AION were significantly different from those of normal controls. No statistical difference was found between A-AION and normal controls. CONCLUSION NA-AION occurs predominantly in small discs while the arteritic form of the disease shows no such preference. Factors related to optic disc structure play a role in the pathophysiology of NA-AION. The occurrence of AION in large optic optic discs should raise the suspicion of temporal arteritis. On the other hand, small optic disc areas do not rule out that vasculitis.