Veterinary ophthalmologists have identified a condition of rapid onset blindness: Sudden Acquired Retinal Degeneration Syndrome (SARDS). Examination of tissue specimens from some patients has indicated that the retinas of these pets are totally destroyed and cannot regenerate. The related blindness occurs rapidly.
Whenever your pet is showing signs of a health issue your first step is to contact your primary care veterinarian. If it is indicated that your pet may suffer from SARDS or another serious condition, a veterinary specialist is available at an ExpertVet certified or affiliated hospital.
Signs and Symptoms
Though the cause of SARDS is currently unknown, the condition can be associated with an increase in thirst, urination, and weight gain in pets. These signs can resolve over time (weeks to months after the onset of blindness) although some dogs are affected longer. It usually occurs in pets that seem to be healthy; however, lab work will often reveal abnormalities such as elevated cholesterol, lipids (fat), or liver enzymes in the blood. The disease normally occurs in middle-aged to older female dogs, but males can also be affected. SARDS may occur in any breed including mixed-breed dogs; however, of the pure-bred dogs, Dachshunds and Schnauzers appear to be overrepresented.
In a dog with SARDS, an examination by a veterinary ophthalmologist would reveal that the dog has normal eyes with no evidence of significant cataract development and no evidence of apparent retinal disease; however, the pet is blind. Correctly diagnosing the cause of a pet’s sudden blindness is important because if systemic disease or optic neuritis is causing the blindness, medication may restore vision. If a brain tumor is determined to be present, then radiation therapy may be necessary to save your pet's life.
Since the retina and ocular examination appear
s normal on initial evaluation with the exception of the dilated pupils, an electroretinogram (ERG) is an essential diagnostic test that can distinguish SARDS from other causes of blindness, such as central nervous system disorders of the optic nerve or brain. An ERG simply involves placing a specialized contact lens on the eye and flashing a series of lights. The dog may be sedated, but awake for this procedure. Each flash of light should stimulate the retina to produce a small electrical response that can be measured by a computer. The response is then compared to normal values.
If your pet has SARDS, the ERG will show an absence of retinal activity. If the retinal activity is normal, then the reason for vision loss may be within the brain or optic nerve. In such cases, additional diagnostic testing or consultation with a neurologist may be recommended to determine the cause of blindness.