This five year old cocker spaniel came to me this morning with a history of gradually failing vision. I asked the students, before we saw the dog, what the likely diagnosis could be. My resident replied PRA, a possible diagnosis with which I agreed. But I didn’t ask what sort of PRA she meant and was surprised to see this retina. What is this disease? The dog is getting clumsier, which could be because of visual deficient – or could it be something else?
Here’s the dog – a rather lovely working cocker spaniel (note the ‘working’ bit!). This is retinal pigment epithelial dystrophy (RPED) or central PRA (note not generalised!) The brown spots in the retina are lipofuscin, deposited because the rpe isn’t adequately dealing with the photoreceptor debris its meant to be phagocytosing. There is also gradually increasing tapetal hyper-reflectivity with the retinal degeneration. Gill Mclellan has done some wonderful detective work uncovering the fact that these dogs are vitamin E deficient, not because of insufficient dietary intake but from a metabolic problem. Read her two papers in the Veterinary Record (Clinical and pathological observations in English cocker spaniels with primary metabolic vitamin E deficiency and retinal pigment epithelial dystrophy. Vet Rec 153:287-92 and Vitamin E deficiency in dogs with retinal pigment epithelial dystrophy.
Vet Rec. 151:663-7). The clumsiness may be because of neurological licofuscinosis and while the retinal changes can only be halted by supplemental vitamin E, we are hoping that the neurological sequelae may be reversed to some extent with the vitamin given orally.