Hereditary retinal degeneration in the Abyssinian cat: Developmental studies using clinical electroretinography

Abstract

Electroretinography was performed in 10 Abyssinian cats, homozygous for a hereditary retinal degenerative disease but still with an ophthalmoscopically normal retina, and in 11 mixed-breed controls, all between the ages of 8 and 104 weeks. A significant reduction of maximum dark-adapted b-wave amplitude was found in affected kittens as young as 8–16 weeks when compared with controls, although there was no major difference in dark-adapted b-wave threshold or implicit time for the b-wave between affected and controls. For cats 33–104 weeks, similar results were obtained except for the b-wave threshold, which was elevated 2.5 log units in one of the affected cats. No significant difference in 30-Hz cone flicker responses were found between affected and controls at any age studied. In the time period 17–32 weeks affected Abyssinian kittens could not be differentiated from controls by means of the electroretinogram. The significant reduction in scotopic b-wave maximum amplitudes in young affected kittens (8–16 weeks) in conjunction with normal thresholds suggests an early drop-out of rods. It is clear that affected kittens can be differentiated electrophysiologically from controls long before there are ophthalmoscopic signs of retinal disease.