Visual evoked potential in dogs and sheep

ABSTRACT:

The visual evoked potential (VEP) is an electro-diagnostic technique that allows assessment of visual pathways. The VEP from 20 adult dogs and 20 adult sheep of both gender was obtained for normative study. Monopolar electrode needles were placed in O₁ and O₂ (active), F_pz (common reference) and C_z (ground). The stimuli were flash at 1Hz. Seventeen dogs and 17 sheep were included in the study because they had auditory potentials with good technical quality. The results from both eyes were grouped, totaling 34 results in each species. The most consistent result in all tests was an electropositive deflection, with a mean latency 55.4ms in dogs (P55) and 63.75ms in sheep (P63). Two negative deflections were also identified: N31 and N75 in dogs, and N42 and N86 in sheep. The methodology used in this study allowed to obtain potential similar to those described in other studies, with little variability, and is useful for evaluation of animals with suspected changes in the central visual pathways.

INDEX TERMS:
Visual evoked potential; neurology; oftalmology; dog; sheep