II. Improved dark adaptation after carotid endarterectomy. Evidence of a long-term ischemic penumbra?

We have reported that dark vision is impaired in symptomatic carotid artery disease and that the impairment correlates with internal carotid artery stenosis. To find out whether this impairment is reversible after carotid endarterectomy, dark adaptation was examined pre- and postoperatively. Twenty-one consecutive patients were examined by dark adaptometry. Two examinations were done for each eye on two consecutive days pre- and postoperatively. Thirty-one matched control subjects were examined under identical conditions. The control subjects did not have clinical evidence of carotid artery disease. Patients and control subjects were free of ophthalmologic disorders. Dark vision frequently improved remarkably after endarterectomy. The average retinal sensitivity to light in darkness on the operated side doubled, and there was also improvement on the nonoperated side. There was no significant change in dark vision in the control subjects, negating a learning effect. The findings suggest the existence of reversible neuronal ischemia secondary to hemodynamic causes or frequent subclinical microembolization. Because the circulatory conditions are optimized, formerly inactive, surviving neurons may regain function.