Analysis of the components of electrically evoked response using a monopolar recording technique.

PURPOSE To assess the significance of the components of the electrically evoked response. METHODS Twenty-three normal subjects, six patients with macular holes, and three patients with retinal artery occlusion were tested. The electrically evoked responses were recorded from an occipital electrode by applying an electric current of 0.3 mA-2.0 mA with a duration of 5 msec and a frequency of 1.85 Hz. RESULTS In the normal subjects, three rhythmic waves (N1P1, N2P2, N3P3) were frequently found with fewer individual differences in their latencies than in flash visual evoked potentials. It was found that the amplitude of N1P1 became larger in proportion to the stimulus strength, and that the amplitudes of N2P2 and N3P3 reached their ceiling peaks. The amplitudes of N2P2 were significantly reduced in the affected eyes of patients with a unilateral complete break of the macula and branch retinal artery occlusion including the macular area. Conversely, in one patient with central retinal artery occlusion, whose visual acuity was good because the cilioretinal artery was patent, the amplitude of N1P1 was significantly reduced in the affected eye. CONCLUSIONS N2P2 in electrically evoked response might originate mainly in the macular area. The analysis of N2P2 may be useful for further clinical applications of electrically evoked response.