Sudden acquired retinal degeneration syndrome (SARDS) is a permanently blinding disease that occurs suddenly, as the name suggests. It is one of the leading causes of incurable canine vision loss diagnosed by veterinary ophthalmologists. Much research has been done to try and discover both the cause and a cure; however, as yet, neither has been found.
The predominant signalment of a SARDS patient is a middle-aged, spayed female, mixed-breed dog. Of the purebred dogs, small breeds are most commonly affected (Box 1). The median age at diagnosis is 7 to 10 years. Often, the dog is moderately overweight.
BOX 1 Top Breeds Affected by SARDS1
- Bichon frise
- Brittany spaniel
- Cocker spaniel
- Miniature schnauzer
HISTORY AND SYMPTOMS
Owners of dogs with SARDS present their pets with the primary complaint of sudden blindness. They often report that their dog bumps into stationary objects, becomes confused in corners, or seems lost in large, open spaces. In these situations, the dog may become anxious and begin vocalizing and/or panting excessively. Astute owners may notice the dog’s pupils are dilated.
Up to 85% of dogs with SARDS have these systemic signs (increased drinking and appetite, increased urination and weight gain). Patients that present with signs of hyperadrenocorticism (Cushing’s disease) should be tested for the disease.
SARDS is typically diagnosed on the basis of a thorough eye exam. Your veterinarian will perform a number of tests to assess your dog’s vision and visual reflexes. The pupils will not respond normally to light and your dog will show a number of other responses consistent with blindness.
The only way to definitively diagnose SARDS is with a test called electroretinography (ERG).
This test involves flashing a bright light in front of the eye and monitoring the electrical activity of the retina. If there is no electrical activity within the retina (a ’flat line’), the dog can be definitively diagnosed with SARDS. However, this test is rarely performed because it requires referral to a veterinary ophthalmologist. Therefore, most cases of SARDS are diagnosed on the basis of history and clinical signs on veterinary exam.
Your veterinarian may perform blood tests, including a complete blood cell count and serum biochemistries. While there are typically no bloodwork changes seen with SARDS, this bloodwork can help rule out other conditions that may cause blindness. Given the correlation between SARDS and Cushing’s disease, your veterinarian may also recommend a test for Cushing’s disease.
SARDS is idiopathic, meaning that we do not know what causes it. Multiple theories have been considered. Some speculate that SARDS may be caused by autoimmune inflammation within the retina, but there is no proof of this theory. The blindness associated with SARDS is due to abnormal function of multiple receptor types within the retina (receptors are specialized cells that convert light into electrical signals that are sent to the brain via the optic nerves). It is unknown, however, whether the abnormality occurs in the receptors themselves, or in the nerves that transmit the signals to the brain
Unfortunately, there is no treatment for SARDS. Various treatments have been tried to restore vision and have failed. A variety of treatments and supplements have been recommended and marketed for this condition, but there is no evidence that any of these treatments offer benefits to affected dogs.
If a dog is noted to have Cushing’s disease during its workup for SARDS, Cushing’s disease can be treated with a variety of medications. Treating Cushing’s disease, however, will not help restore the dog’s vision.
Blind dogs can live very happy lives. Owners of dogs with SARDS report that if anything, their relationship with their pet improved after the sudden blindness. It does take some time—up to a couple of months—for the dog to adjust to being blind, and adjustment is harder with sudden vision loss than with gradual blindness. However, dogs have cognitive mapping skills and can easily memorize their home environment. They may still become disoriented outside of their home or yard.
A few accommodations may need to be made for safety reasons. Blind dogs should be kept in a fenced yard or on a leash when outside. Access to bodies of water should be restricted. Owners should avoid moving furniture as much as possible to avoid confusing the dog’s mental map of the environment and may want to consider padding sharp corners to prevent injuries. Other changes can help dogs with their mental map. For example, different textured surfaces can be used to indicate food, water, door, stairs, walls, or fences
Several websites provide advice for living with blind dogs, such as providing toys that make noise or
have a strong scent (Box 2).
BOX 2 Recommended Resources for Owners
- Blind Dogs Can Have Normal Lives Too!
- Blind Dog Support
- Enable Your Pet
- Walkin’ Pets