Carotid occlusive disease. Effect of bright light on visual evoked response.

Four patients had severe carotid artery occlusive disease associated with ipsilateral visual blurring and exposure to bright light. Attenuation of the visual evoked response was noted after patients were exposed to an artificial source of light for 30 s. No significant abnormality of the visual evoked response was seen in the asymptomatic eyes or in the 16 eyes of eight control subjects, some of whom had carotid artery occlusive disease associated with ipsilateral venous stasis retinopathy. We concluded that ischemia of the macular region is necessary to produce these visual symptoms and that local retinal blood flow has been reduced to the flow threshold of electrical failure. These findings provide objective documentation of an abnormality that may be associated with an important symptom indicative of severe carotid artery occlusive disease.