This Siamese cat is presented to you with the owner having been concerned about its vision since they moved house and the cat suddenly couldn’t find its way around. What is the lesion and why has the cat had this apparently acute loss of vision?
This is tapetal hyper-reflectivity demonstrating that there is retinal degeneration. Inherited retinal degeneration is seen far less in the cat than in the dog where progressive retinal atrophy is common in several breeds. The Siamese is seen more commonly than other cat breeds with these signs (Giuliano and van der Woerdt Feline retinal degeneration: clinical experience and new findings (1994-1997). J Am Anim Hosp Assoc. 1999 35:511-4) but no specific mutation has been defined in this breed. This paper specifically makes the point that cats adapt very well to blindness and this is what seems to have been the case here. The retinal degeneration is a chronic not acute change; a cat with these signs may have been blind for a long time but well adapted to its surrounding. Only a change of environment showed its defective vision. The owner can be reassured that the cat will readapt quickly and show no ill effects from its blindness.