Sudden Acquired Retinal Degeneration Syndrome (SARDS) is characterized by sudden vision loss in the dog. As the name implies, this disease affects the retina, which is the back part of the eye responsible for sending visual signals to the brain for interpretation. Due to an unknown cause, SARDS patients suddenly lose retinal function and become blind. There is subsequent degeneration or atrophy of the retina that can lead to other complications. In addition to a sudden loss of vision, many owners notice enlarged pupils, as well as, increased appetite and thirst.
In all patients with acute vision loss, an electroretinogram (ERG) is recommended. This test allows for assessment of retinal function, and if the result is negative, it provides a definitive diagnosis of SARDS. An electroretinogram is a non-invasive test that involves placing a specialized contact lens on the surface of eyes that have been numbed with topical anesthetic drops. Some pets require tranquilization or light sedation to reduce movement that can affect the results. After a period of dark adaptation, a standardized series of light flashes are created to stimulate the photoreceptors of the retina. The photoreceptors create an electrical signal that is detected by the contact lens and recorded by a computer. A normal retina produces a waveform, much like an EKG for the heart. In a SARDS patient, the normal electronic responses of the retina are extinguished and no waveform can be detected. In the early stage of the disease, the retina appears normal on ophthalmic examination. After a period of months, signs of degeneration of the retina can be observed on ophthalmic examination.
This syndrome most often occurs in middle-aged female spayed adult dogs No breed is known to inherit the condition, but some breeds appear to be more susceptible than others – including dachshunds and miniature schnauzers. Affected animals are generally in good health, but as described above, some dogs may have a recent history of unexplained weight gain, lethargy, pacing, panting, increased appetite, increased consumption of water and/or increased urination. Blood work is recommended to rule out any systemic problems, such as a condition called Cushing’s that is characterized by high blood cortisol. If affected dogs have systemic problems, an internal medicine consultation may be recommended. The etiology, or underlying cause, of SARDS is currently unknown; however, multiple laboratories are conducting research to find the cause. Possible theories for this syndrome include endocrine disorders, autoimmune disease, toxicity, infection, neoplasia, etc.
Unfortunately, there is currently no proven treatment or prevention for SARDS and the blindness it causes is irreversible. The good news is that SARDS is not a painful condition and that it does not reduce your dog’s life expectancy. Many dogs adjust very well to being blind. It may take a few weeks to months for your dog to fully acclimate, but a recent publication reported that owners of dogs with SARDS find their pets to have a very good quality of life. Animals should also be monitored long-term complications, such as secondary cataract formation or glaucoma that can be painful. If signs of these conditions are seen, prophylactic medical therapy may be required. Safety precautions should be taken for all visually-impaired pets, particularly around swimming pools, stairs, roads, strange dogs, etc. There are many resources for owners with blind pets to help the owners adjust to living with blind dogs, as this condition can sometimes be more difficult for the owners than their dogs.