Degeneration of the Image Forming Part of the Eye in Dogs

Take your dog to the veterinarian if you notice any signs of vision loss.

• Nyctalopia – decreased vision at night
• Dilated pupils
• Decreased pupillary response to light
• Gradual vision loss
• Sudden blindness
• Inability to judge distances
• Difficulty climbing stairs
• Missing details such as small objects

Types

Some of the many types of retinal degeneration are listed below, as well as the breed which they are known to affect. Any dog could develop this problem.

Progressive retinal atrophy (PRA)

can be classifed into four types:

• Photoreceptor Dysplasia

   

• Becomes apparent in the first year (autosomal recessive trait)
• Irish settlers, Collies, Norwegian Elkhounds, Miniature Schnauzers, Belgian Sheepdogs
• Photoreceptor degenerations 
• Signs develop in the first 3-5 years (autosomal recessive trait)
• Miniature and Toy Poodles, Samoyeds, English and American Cocker Spaniels, Labrador Retrievers, Tibetan Terriers, Akitas, Tibetan Spaniels, Papillons, English Springer Spaniels, Miniature Longhaired Dachshunds 
• Photoreceptor degeneration (x-linked trait)

   

• Siberian Huskies
• Photoreceptor degeneration (autosomal dominant)

   

• Old English Mastiffs, Bull Mastiffs

Retinal pigment epithelial dystrophy or central progressive retinal atrophy (CPRA)

• Similar to PRA, but degeneration begins in the epithelial layer of the retina
• Labrador Retrievers, Collies, Shetland Sheepdogs, Briards

Sudden acquired retinal degeneration (SARD)

• Signs develop between 7-14 years, more common in females
• Dogs often experience increased appetite and weight gain just before the disease becomes apparent

Age-related macular degeneration

• Usually occurs in dogs over 7, more common in females  
• There may be some genetic component, but exposure to environmental factors and overall health play a big part.

Most types of retinal degeneration are caused by one of three factors.

• Inherited
• Age-related
• Idiopathic

If your dog is developing symptoms of vision deterioration or night blindness, the veterinarian will carefully examine the eye. Retinal degeneration can often be detected with traditional ophthalmoscopy, but electroretinography offers a more complete measurement of retinal function. In some cases of PRA, cataracts may already be present, which can make it difficult to see the retina. In the case of CPRA, changes in pigmentation in the outer layer of the retina can sometimes be diagnosed early, before dogs start to show symptoms, so dogs at risk should be evaluated even if they are not experiencing vision loss. SARD is also diagnosed with these methods, but in most cases vision loss is quite severe before retinal damage can be detected. Older dogs experiencing mild vision loss will be evaluated the same way. Various vision tests may be necessary to determine the range of your dog’s vision and ascertain the extent of damage.

Other potential causes of vision loss will need to be ruled out, such as glaucoma, age-related cataracts, or in the case of SARD’s, brain tumors and inflammation. Blood and urine tests will be necessary to eliminate some possibilities and ascertain the state of your dog’s health. Sedation or anesthetic could be required for dogs that will not tolerate an eye exam.

The veterinarian will need to know your dog’s breed and family history since many forms are inherited. In some cases, dogs can be tested for genes that are known to cause retinal degeneration before symptoms develop. If your dog belongs to a breed with a known inherited problem, this possibility should be discussed with a veterinarian.