Effect of bilateral asymptomatic internal carotid artery stenosis on electrophysiological function of the retina and optic nerve

Aim
This study was designed to assess the bioelectrical function of the retina and optic nerve in patients with bilateral, asymptomatic, yet hemodynamically significant internal carotid artery stenosis.

Material and methods
Twenty-six eyes of 13 subjects with bilateral internal carotid artery stenosis and 34 controls were analyzed. Pattern electroretinogram, full-field electroretinogram and pattern visual evoked potentials, as well as routine ophthalmic examination were performed.

Results
The pattern electroretinogram P50 and N95 wave amplitudes were significantly reduced in patients (p = .0001 and p < .0001 respectively) as compared to controls. The full-field electroretinogram rod b-wave, rod-cone a-wave and b-wave amplitudes were reduced (p = .03, p = .02 and p = .03, respectively) and the implicit times of rod b-wave and rod-cone b-wave were significantly prolonged (p = .01 and p = .02, respectively), whereas the oscillatory potential wave index was reduced (p = .009) in patients as compared to controls. When analyzing cone responses, 30-Hz flicker wave amplitudes were reduced (p = .01) and cone a-wave and b-wave single flash implicit times were significantly prolonged (p = .0009 and p = .02, respectively) in patients as compared to controls.

Conclusions
Our study demonstrated that retinal bioelectrical function is negatively affected by internal carotid artery stenosis despite the absence of objective clinical signs and symptoms of ocular ischemia.