Electroretinogram and visual-evoked potential measurements in Holstein cows.

The electroretinogram (ERG) and flash visual-evoked potential (FVEP) were recorded from 25 Holstein cows in a clinical setting without dark adaptation. Latencies to the a and b waves of the ERG were measured bilaterally. The ERG recordings were between the lower eyelid of the stimulated eye and the vertex, with ground on the nuchal crest. Stimuli for ERG and FVEP were 1.5 flashes of white light/s. Recorded ERG were highly consistent and repeatable. The average latencies for the a and b waves were 14 and 30 ms; the mean ab amplitude was 43 microV. The FVEP were recorded bilaterally between the middle of the interocular line and the midpoint of the nuchal crest, with ground on the vertex. The FVEP measurements included latencies to 5 alternating positive and negative peaks (P1, N1, P2, N2, and P3) and 4 peak-to-peak amplitudes (P1 to N1, N1 to P2, P2 to N2, and N2 to P3). The P2 peak was consistently the most prominent. Average latencies for the 5 peaks were 46, 64, 86, 106, and 137 ms for P1, N1, P2, N2, and P3, respectively. The FVEP peak-to-peak amplitudes had a high variability.