[Monocular photopsia preceding with neovascular glaucoma due to internal carotid artery occlusion; a case report]

We described a 67-year-old right handed man with a left internal carotid artery occlusion, who developed monocular photopsia that supervened neovascular glaucoma. He had an antecedent transient motor aphasia. His photopsia, exaggerated by light, persisted intermittently. Orbital bruit was obtained on the left, more clearly during the photopsia. Brain MRI, cerebral angiography, and duplex sonography of carotid and ophthalmic arteries indicated left internal carotid artery (ICA) occlusion with collateral circulation through the ophthalmic artery. Visual evoked potentials (VEPs) revealed a prechiasmal disturbance of the optic pathway of the left side. The patient had carotid endarterectomy of the left ICA, and his visual disturbance has gradually improved. Ocular symptoms due to ICA ischemia are commonly transient visual loss with dark background known as amaurosis fugax. Neovascular glaucoma is sometimes complicated with carotid artery occlusion. However, photopsia associated with carotid artery occlusion is rare. Photopsia mimics scintillating scotomata, but the latter precedes migraine and is biocular and homonymous, ascribable to spreading depression from the occipital lobe. Retinal or prechiasmal optic pathway might be influenced by poor circulation of the ophthalmic artery. In addition, disturbance of light adaptation due to retinal hypoperfusion may be possible reason. Neovascular glaucoma is intractable, once developed. Therefore, atypical scintillating visual disturbance must be recognized as a sign of carotid artery insufficiency and supervened glaucoma to prevent it.