Retinal folds are generally genetic in origin. The fold form of retinal dysplasia is less severe than the geographic and displaced types. Often these little blind spots don't really affect a dog's vision. They're congenital, or present at birth, and don't worsen with age. Sometimes the retinal folds disappear as a mildly affected dog gets older. Less often, retinal folds result from puppies affected in utero with parvovirus or herpesvirus.
The dog's retina, located at the rear of the eye, receives light and sends signals to the brain via the optic nerve. The Veterinary Medical Database describes retinal folds as occurring when "two primitive layers of the retina do not form together properly." The geographic form is more serious, involving thinning as well as folding. In the worst form of retinal dysplasia, the two layers don't come together at all, causing the retina to be detached.
Breeds prone to hereditary retinal folds include the akita, Cavalier King Charles spaniel, German shepherd, Doberman pinscher, cocker spaniel, Belgian malinois, bull terrier, Rottweiler, mastiff, Norwegian elkhound, Samoyed, border terrier, Labrador retriever, Gordon setter, Australian shepherd, Old English sheepdog, cairn terrier, soft-coated wheaten terrier, Bedlington terrier, Sussex spaniel, Pembroke Welsh corgi, collie and clumber spaniel.
Puppies with geographic folds obviously have some vision trouble once their eyes open at about the age of two weeks. Those with retinal folds appear to see normally, so only a veterinary examination can detect the condition. That examination must take place after the puppy reaches the age of 4 months, because that's when his retina fully matures. The vet might want to take another look when the puppy reaches the age of 6 months, because the actual eye has grown, making examination easier.
Even though retinal folds don't cause problems for most dogs, the condition is considered a defect. The only way to prevent retinal folds from occurring in future generations is to avoid breeding dogs with this condition or with the genetic markers for it. In Samoyeds and Labrador retrievers, retinal folds often accompany a condition called oculoskeletal dysplasia, or OSD. This skeletal abnormality results in dwarfism, while retinal detachment occurs as the dog gets older. A simple cheek swab test can detect whether a dog is a carrier (an unaffected animal capable of passing on the genetic defect). While a carrier won't exhibit OSD, the dog probably has retinal folds. Carriers bred to dogs without the OSD and retinal fold gene might produce other carriers, but not affected dogs. It is also possible for puppies to acquire retinal folds from prenatal exposure to viruses, but responsible breeders will already have vaccinated the mother dog for those illnesses.
By Jane Meggitt
About the Author
Jane Meggitt has been a writer for more than 20 years. In addition to reporting for a major newspaper chain, she has been published in "Horse News," "Suburban Classic," "Hoof Beats," "Equine Journal" and other publications. She has a Bachelor of Arts in English from New York University and an Associate of Arts from the American Academy of Dramatics Arts, New York City.