Sudden Acquired Retinal Degeneration (SARD)
Sudden acquired retinal degeneration (SARD) is a retinal disease seen in Shar-Pei as well as other breeds of dogs. Remember the retina is the photoreceptor layer of the eye which is responsible for converting visual images to electrical signals. These signals are transmitted to the brain where the image is processed. This condition leads to a very sudden onset of blindness which occurs over a period of a few days to several weeks. The retina is normal when viewed with an ophthalmoscope, but there is a loss of photoreceptor activity as evidenced by a diminished electroretinogram (ERG). The ERG is a test which measures the electrical activity of the retina. Synonyms for SARD are “toxic metabolic retinopathy” and “silent retina syndrome”. Shar-Pei with SARD are usually middle-aged females many of whom are overweight and may have symptoms of Cushing’s disease or hyperadrenocorticism – increased water consumption, increased urination, panting, increased appetite, etc. Often there are laboratory changes in the blood tests consistent with hyperadrenocorticism such as an increase in liver tests such as the alkaline phosphatase, alanine transaminase (used to be the SGPT) and cholesterol. Some of these dogs will have abnormal ACTH stimulation or low-dose dexamethasone suppression tests confirming hyperadrenocorticism. I must emphasize that a link between SARD and hyperadrenocorticism has not been proven although I would recommend that all Shar-Pei with SARD be evaluated for hyperadrenocorticism. Treatment for hyperadrenocorticism will not result in a return of vision. Not all dogs with SARD have hyperadrenocorticism, but the percentage is higher than in the normal dog population. The cause of SARD is not known at this time, but one theory suggests that perhaps an abnormal corticosteroid has a role in the disease process as well as being involved in the hyperadrenocorticism. There is no treatment for SARD and the dog will be permanently blind. Your veterinarian should rule out other causes of blindness in Shar-Pei which include glaucoma, retinal detachment (sometimes accompanying hypertension with kidney disease), pigmentary keratitis, optic neuritis, etc.