Disorders of the Retina, Choroid, and Optic Disk (Ocular Fundus) in Dogs

Collie eye anomaly is an inherited eye defect present at birth in varying degrees in rough- and smooth-coated Collies. It also occurs in Shetland Sheepdogs, Border Collies, Australian Shepherds, Lancashire Heelers, and the Nova Scotia Duck Tolling Retriever. The main abnormality is an area of the choroid or the retina and choroid that fails to develop fully. More severely affected dogs may also have abnormalities close to where the optic nerve enters the eye, and some will have detachment of the retina. Blood vessel ruptures within the eye may occur. Vision is not noticeably affected unless detachment of the retina is present.

An abnormal development of the retina called retinal dysplasia is present at birth and may arise from trauma, genetic defect, or damage occurring while in the womb from conditions such as viral infections. Most forms of retinal dysplasia in dogs are inherited. Viral infections of the mother (for example, herpesvirus in dogs), especially during early fetal development, can result in many eye abnormalities with retinal dysplasia in puppies. Retinal dysplasia is thought to be inherited in American Cocker Spaniels, Beagles, Labrador Retrievers, Rottweilers, and Yorkshire Terriers. Small areas of retinal dysplasia may not cause any signs or interfere with vision. Generalized retinal dysplasia with detachment of the retina, visual impairment, or blindness is inherited in English Springer Spaniels, Bedlington Terriers, Sealyham Terriers, Labrador Retrievers, Doberman Pinschers, and Australian Shepherds. Other eye abnormalities, including abnormally small eyes and cataracts that are present at birth, often occur together with the generalized forms of retinal dysplasia.

Progressive retinal atrophy is the name for a group of diseases that cause degeneration of the retina. This includes inherited abnormalities of the light-sensitive cells (photoreceptor dysplasia) and degenerations that have similar signs. The inherited photoreceptor dysplasias in which signs develop in the first year occur in Irish Setters, Collies, Norwegian Elkhounds, Miniature Schnauzers, and Belgian Sheepdogs. The inherited photoreceptor degenerations in which signs develop at 3 to 5 years occur in Miniature and Toy Poodles, English and American Cocker Spaniels, Labrador Retrievers, Tibetan Terriers, Miniature Longhaired Dachshunds, Akitas, and Samoyeds. Progressive retinal atrophy is also inherited in Siberian Huskies and Bull Mastiffs. Many other breeds of dogs are also suspected of having inherited progressive retinal atrophy.

The first sign of progressive retinal atrophy is usually night blindness. This progresses to total blindness over a period ranging from months to years. Cataracts are common late in the course of progressive retinal atrophy in many breeds and may mask the underlying disease of the retina. No effective treatment is available, although DNA tests have been developed to detect carrier and affected dogs before signs develop in many breeds.

This type of retinal degeneration occurs in Labrador Retrievers, smooth and rough Collies, Border Collies, Shetland Sheepdogs, and Briards. The condition is inherited in Labrador Retrievers. In many cases, early eye examinations can detect this disease before signs are apparent. Progressive vision loss occurs gradually over several years. Cataract formation occurs late in the disease. There is no treatment. Recent studies suggest systemic vitamin E disorders may also be important in the develop-ment of this disease complex.