Blackouts in one eye with numbness or motor symptoms on the opposite side of the body is now a well-recognized syndrome resulting from carotid occlusion.1 Usually the diagnosis can be established ophthalmodynamometrically by finding relatively lower retinal arterial pressures on the affected side. What then are the causes of blackouts not resulting from carotid occlusion? The present paper reports a study of patients in whom blackouts were a presenting symptom but in whom the retinal arterial pressures and other cognate signs made it seem unlikely that carotid occlusion was the cause for their symptoms.
The finding of retinal arterial pressures which were equal in the 2 eyes and in the normal range does not of course rule out the possibility of carotid occlusion. Nor does a significant inequality in the arterial pressures in the 2 eyes necessarily indict a carotid occlusion. Nevertheless, those cases of transient monocular blackouts wherein
COGAN DG. Blackouts Not Obviously Due to Carotid Occlusion. Arch Ophthalmol. 1961;66(2):180-187. doi:10.1001/archopht.1961.00960010182007