Utveckling av metod för utvärdering av synnervens funktion hos häst

Abstract: VEP, visual evoked potential is an electrophysiologic test that can be used for evaluating the higher visual pathways. The aim of this study was to investigate if it is possible to adapt this method to horses. This method could have a clinical use in addition to the existing diagnostic methods that are available to evaluate vision in horses. Firstly, this study contains a summary of relevant studies done on animals and, secondly, an experimental part where the possibility of recording VEP in nonsedated and sedated horses is investigated and where to position the recording electrode to obtain the best results. Our results show that it is possible to record VEP in horses in a clinical setting. VEP was best recorded in the sedated horse to avoid movement artifacts and other disturbances. The best signal was obtained when the active electrode was positioned on top of the nuchal crest. When the active electrodes were positioned lateral to the midline, isolation of signals from the right and left hemispheres was possible. The electrodes were easy to apply, but the impedance had to be checked to evaluate the connection between the electrodes and the skin. Akinesia of the eyelids had to be induced to reduce blink artifacts. Because this study just contains results from VEP-recordings from two horses, further studies are needed that will provide normative data and assessment of its clinical use.