Sudden acquired retinal degeneration

Sudden acquired retinal degeneration (SARD) is 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.

The cause of SARD is considered to be idiopathic, but possibly involves either autoimmune disease, a toxin, or Cushing's disease. Symptoms include sudden permanent blindness (sometimes developing over several days), 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, 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. 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.