Jämförande studie av normal ERG-svar hos tre olika hundraser

Sammanfattning: The purpose of this study was to compare normal electroretinographies (ERGs) from three different canine breeds in order to evaluate if there were any marked similarities or differences between these breeds as to ERG responses. It is known that healthy dogs from different breeds but also dogs within the same breed but in different age categories may have different appearances of their ERG responses. This may be a problem when evaluating if an ERG is normal or not from a dog within a breed not previously examined. Because of this it is important to obtain normal values for each breed and age group in order to be able to use these for later comparisons of ERGs obtained from individuals affected with various retinal diseases. In this study we have chosen to examine dogs within the three breeds: Labrador Retriever (LR), English Springer Spaniel (ESS) and Chinese Crested Dog (CCD). All of these breeds may be affected with hereditary retinal diseases such as Progressive Retinal Atrophy (PRA). It is possible that ERG-responses vary due to a number of different factors. Some of these are: the wavelength, the intensity and the duration of the light stimulus used, the sedative or anaesthetic agent used, the ERG equipment used and if the eye is dark adapted or light adapted before the examination starts. Variations in results and errors can be minimized by using a fixed protocol, the same ERG-equipment and the same kind of sedation or anaesthesia every time. Even though the same techniques are used there are differences in regards to various species, breeds and age-groups and comparisons should therefore always be done with normal animals of the same species, breed and age-group if possible. The results of the present study show that the ERG responses from different breeds do differ markedly. Therefore, it is not possible to compare a response from one breed to another even though the same kind of protocol, ERG equipment and sedation is used. Both a- and the b-wave amplitudes differ substantially between the different breeds. The implicit time of the ERG a- and b-waves is relatively similar between the breeds but due to differences in amplitudes it is still not possible to compare a response from one breed to another.