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Issue Description
A disease in dogs causing sudden blindness. It can occur in any breed, but female dogs may be predisposed. Approximately 4000 cases are seen in the United States annually.
Other Names
Sudden Acquired Retinal Degeneration

The cause of SARDS is considered to be idiopathic and the veterinary community is divided as to its cause, but the disease possibly involves autoimmune disease, toxins, elevations in adrenal sex hormones or Cushing's disease.

Symptoms include sudden permanent blindness, but may occur more slowly over several days, weeks or months, dilated pupils, and loss of the pupillary light reflex. Other symptoms commonly seen are similar to those seen with Cushing's disease and include increased water consumption and urination, weight gain, confusion, restlessness, behavioral changes and lethargy. These symptoms may develop over a few months preceding the onset of SARD. Despite similar symptoms and blood test results to Cushing's disease, evaluation of dogs with SARD did not reveal any tumors in the pituitary or adrenal glands. However, endocrine testing (i.e., Canine Adrenal Panel at the University of Tennessee College of Veterinary Medicine Endocrinology Service) often shows elevations in adrenal sex hormones. Clinical signs and disease progression vary markedly among individual animals, depending on the number and type of hormones that are increased, the degree of hormone elevation, and the age of the dog. Autoimmune disease as a cause has also been called into question because of a lack of antiretinal autoantibodies in dogs with SARD in one study.

Examination with an ophthalmoscope will initially show no changes, but in a few months atrophy of the retina will resemble the appearance of progressive retinal atrophy. Pathologically, there is a loss of the rod and cone cells followed by degeneration of other layers of the retina. The retinal degeneration appears to be related to apoptosis of these cells. SARD must be distinguished from other causes of sudden blindness that have no visible pathology, including retrobulbar optic neuritis, a tumor at the optic chiasm, or other central nervous system diseases. Electroretinography is useful to definitively diagnose SARD.

Currently there is no approved treatment, although the use of intravenous immunoglobulin has been investigated due to similarities between SARD and human immune-mediated retinopathy.

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