The following article is reprinted by permission, Dr. Denise Lindley, DACVO/author and appeared in the January-June, 1993 issue of "CERF News". Submitted by ACVO Ophthalmologist Dr. Lisa A. Meek who practices in Stuart, Florida with an addendum from her on retinal folds which follows the article.
The retinal dysplasias are a diverse group of conditions in which the retina does not develop properly. Retinal dysplasia may arise spontaneously, often as the expression of a genetically determined trait. Other causes of retinal dysplasia that are less commonly identified in dogs include dietary, toxic, infectious, and physical insults.
Inherited retinal dysplasias have been described in the veterinary literature in the American Cocker Spaniel, Australian Shepherd, Bedlington Terrier, Beagle, Doberman Pinscher, English Springer Spaniel, Labrador Retriever, Rottweiler, Sealyham Terrier, and Yorkshire Terrier. According to the 1991 CERF Database, retinal dysplasia was seen by veterinary ophthalmologists in 52 breeds of purebred dogs.
The clinical manifestations of retinal dysplasia vary between breeds and can range from a few retinal folds (seen as lines or curves on the fundus or the back part of the eye) to geographic lesions (areas of retinal disorganization in the central fundus and local retinal detachment) to generalized retinal detachment.
Dogs affected with multifocal retinal dysplasia generally have no significant visual abnormalities. But some breeds of purebred dog have more than one form of retinal dysplasia. For example, retinal dysplasia in the English Springer Spaniel can present as retinal folds or geographic lesions. Dogs with geographic lesions because of the local retinal detachment and resulting local retinal degeneration have variable vision loss. In the most severe cases generalized or full retina detachment, the dogs are blind.
Dysplastic lesions are not progressive and become less prominent on ophthalmoscopy as the dog ages. Retinal detachments are usually identified before the animal is six months old.
Retinal dysplasia can occur with other ocular anomalies including microphthalmia (developmentally small eye), intraocular hemorrhage, corneal pigmentation, and nystagmus.
In the Labrador Retriever, retinal dysplasia and skeletal abnormalities can occur. In this breed, the syndrome is believed to be caused by a single autosomal gene that has recessive effects on the skeleton and incomplete dominant effects on the eye. Heterozygous Labradors have clinically normal skeletons and mild ocular abnormalities. Homozygous Labradors have limb deformity and either mild or severe ocular abnormalities.
It is important to remember that the inheritance of the retinal dysplasia in most breeds has not been studied. It is unclear in many breeds that have been identified with retinal folds whether these same breeds can develop the more severe forms of retinal dysplasias.
Addendum from Dr. Lisa A. Meek -- Focal retinal folds that are occasionally seen in the eyes of young pups (less than 12-14 weeks of age) may disappear as the eye grows. This probably represents an uncoordinated growth of the inner and outer layers of the optic cup. (The optic cup is an early developmental stage of the eye). These types of folds have usually been associated with small eye sizes, such as in the Collie and Shetland Sheepdogs. The significance of focal retinal folds in puppies of breeds that do not have an identified inherited dysplasia is unknown.