(Sudden Acquired Retinal Degeneration Syndrome)
- Sudden acquired retinal degeneration syndrome (SARDS) is a leading cause of incurable canine vision loss diagnosed by veterinary ophthalmologists.
- SARDS is characterized by acute onset of blindness due to loss of function in part of the retina, the photoreceptors. Because the photoreceptors are responsible for transforming light energy into a neural signal, loss of function of these cells rapidly leads to vision loss.
- Upon exam, the veterinary ophthalmologist may initially see that the back of the eye looks nearly normal. By using a diagnostic test that measures the electrical activity generated by the retina (called an electroretinogram, or ERG), the clinician can evaluate the health of the retina. In SARDS, the electrical activity in the retina is extinguished, whereas the ERG may be normal in certain other diseases that can also cause sudden vision loss.
- SARDS is most commonly diagnosed in female mixed breed dogs, although Dachshunds, miniature Schnauzers, Pugs, and other small breeds seem to be overrepresented.
- The average age of onset is 7-10 years.
- Many patients are moderately overweight.
CAUSE OF SARDS
- The cause of SARDS is unknown.
- It remains controversial as to whether a diagnosis of SARDS is being used to describe multiple disease processes.
- No clear environmental risk factors have been identified as causing SARDS, despite speculation of increased number of cases in winter months or following stressful events.
- Most patients demonstrate clinical signs and laboratory abnormalities suggestive of hyperadrenocorticism and/or increased adrenal sex hormone levels. These can include increased appetite and thirst, increased urination, and lethargy. These abnormalities may resolve over several months.
- A neuroendocrine disorder has been suggested as a potential cause of SARDS. This is supported by the observation that many patients lose their sense of smell along with their vision.
- Autoimmune disease – an illness that occurs when the body attacks its own tissues- has also been proposed as a cause of SARDS, though SARDS patients do not respond to traditional immunosuppressive therapy used to control most other autoimmune diseases.
- Most dogs are more cautious, less playful, and more lethargic during the initial few months of adjustment.
- Clinical signs of generalized retinal degeneration usually become evident on ophthalmic examination in most patients several months after the onset of SARDS.
- Research studies of affected eyes reveal that within a few weeks of the onset of SARDS, retinal damage is limited to extensive loss of the photoreceptors, though patients are already functionally blind. Degeneration of the remaining retinal layers progresses over several months to years.
- Unfortunately, there is currently no effective treatment for SARDS that is supported by published clinical trials.
In 2014, the American College of Veterinary Ophthalmologists’ Vision for Animals Foundation (VAF) hosted a Think Tank to compile current information on SARDS and to recommend future SARDS research.
In October 2015, the VAF awarded a grant, in the amount of $29,948, to Dr. Freya Mowat of North Carolina State University, for research to address SARDS. The title of the two-year study is “Defining the effect of immune-mediated damage to the pineal gland in the etiopathogenesis of sudden acquired retinal degeneration syndrome (SARDS) in dogs”. Co-investigators are: Drs. Katherine Lunn, Natasha Olby, and Gianluca Tosini.