Sudden acquired retinal degeneration syndrome (SARDS) is a disease that causes rapid blindness in dogs–usually, within a few days to a couple of months. For some unexplained reason, the cells in the dog’s retina start breaking down.
The disease can be diagnosed with electroretinography—a test similar to an EKG. While the dog is under anesthesia, electrodes are placed on the cornea to detect activity in the retina. A normal eye produces tracings with peaks and valleys. In dogs with SARDS, the tracings are flat.
Adding to the mystery is the fact that about 75% of the dogs with SARDS also have Cushing’s disease. The symptoms include increased thirst, accidents in the house, an unusually big appetite, pot-bellied appearance, and excess panting. The condition is due to excess production of the hormone cortisol by the dog’s adrenal glands, two small organs that sit on top of the kidneys. While brain or adrenal gland tumors are the most common cause of canine Cushing’s disease, dogs with SARDS don’t have them.
Veterinarians use blood tests to diagnose Cushing’s disease. The most common, the dexamethasone suppression test, takes a full day. First, a blood sample as taken as a baseline measure. Then a synthetic cortisone drug—dexamethasone–is injected and follow-up samples are taken throughout the day. If the dog has normal adrenal function, cortisol production drops. A dog with Cushing’s disease continues to make high levels of the hormone.
Drug treatment can regulate a dog’s cortisol production, keeping the hormone at normal levels. However, it’s important that a veterinarian follow the dog closely because it’s easy to over- or underdose an animal, causing added health problems. Serious side effects are possible, too, and require careful monitoring. The drugs must be given daily and can be costly.
The good news for owners of dogs with SARDS and Cushing’s disease is that treatment of the adrenal problem can offer a dog a longer life of higher quality.
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