Although listed by the Kennel Club as a condition found in Rough and Smooth Collies, the incidence in the United Kingdom is very small, but owners do need to be aware of it as it is more common abroad. There are two main types that affect collies:
Retinal Pigment Epithelial Dystrophy (RPED) that is more commonly known as Centralised Progressive Retinal Atrophy (CPRA) and is a mature onset condition that results in slowly deteriorating vision and eventual blindness. Mode of inheritance is not known but it is thought that it may be caused by a metabolic imbalance. The incidence has greatly reduced over the years and it is thought that modern quality feeds with added vitamin E may be the reason.
It is still recommended by the BVA and KC that dogs are eye checked annually from about 18 months of age as deteriorating vision can be halted by treatment with Vitamin E (no improvement can be expected for lost vision however). There is no DNA test for this condition (CPRA) and it is the PRA most associated with Smooth Collies in the UK.
Generalised PRA or Rod/Cone Dysplasia type II (rcd2)
This is more common in American-bred collies and is an early onset autosomal recessive inherited disease similar to the early-onset form of human Retinitis Pigmentosa. Night blindness is the earliest clinical sign, detectable in six week old puppies, and affected dogs eventually become totally blind and cataract formation is common. There is no cure. There is a DNA test for this condition (GPRA) and the laboratories list it as PRA-rcd2.