 Optical coherence tomography (OCT) may also be used to confirm the diagnosis of CRAO.CRAO can be classified based on it pathogenesis, as arteritic versus non-arteritic.Non-arteritic CRAO is most commonly caused by an embolus and occlusion at the narrowest part of the carotid retinal artery due to plaques in the carotid artery resulting in carotid retinal artery atherosclerosis.