A prospective study of acute central retinal artery obstruction. The incidence of secondary ocular neovascularization. We conducted a prospective study to determine the incidence of ocular neo-vascularization following acute central retinal artery obstruction. Only patients initially evaluated within 7 days of visual loss were eligible. Any patient with pre-existing ocular neovascularization or clinical evidence of the ocular ischemic syndrome noted at the initial evaluation was excluded. During the 18-month study, 33 consecutive patients were enrolled. Six patients subsequently developed neovascularization of the iris, an incidence of 18.2%. In these six patients, neovascularization of the iris appeared as early as 12 days to as late as 15 weeks following the artery obstructions. Five of the six patients (15.2% of the total) later developed neovascular glaucoma. Another patient in this series developed neovascularization of the optic disc without neovascularization of the iris, an incidence of 3.0%. Only two of the seven patients with ocular neovascularization had ipsilateral hemodynamically significant carotid artery disease as determined by noninvasive carotid artery testing. This study confirms results of previous retrospective studies that the incidence of ocular neovascularization after central retinal artery obstruction is higher than commonly thought. It also shows that, in the majority of cases, carotid artery disease is not responsible for the neovascularization seen after central retinal artery obstruction. 