New Treatment Options and Diagnostic Test Now Available for Dogs Diagnosed with Degenerative Eye Dis
Frustrated by limited treatment options, Sinisa Grozdanic, DVM, PhD, set out to find a cure for Sudden Acquired Retinal Degeneration Syndrome (SARDS), a condition that affects thousands of dogs each year.
An immune-mediated disease, SARDS is caused by localized intraretinal production of autoantibodies that attack retinal neurons, said Grozdanic, who adds that because some patients have other systemic signs of disease like Cushing’s, veterinary ophthalmologists and students at Iowa State University have not ruled out systemic involvement. SARDS is not breed-specific, and similar to immune-mediated retinopathy in humans, it can strike at any age and cause irreversible blindness.
Recently, a new treatment option has provided hope for practitioners and specialists.
Professionals are optimistic about the use of intravenous immunoglobulin (IVIg) infusions, which returned limited sight to two dogs last April. Grozdanic and his team also created Collorimetric pupil light reflex evaluation, a diagnostic test being used in specialty practices that isolates SARDS from other optic nerve diseases.
For Bill Miller, DVM, MS, DACVO, the research and new diagnostic test is promising. “The work is in its infancy but it will expand and provide therapeutic options that we can give to patients,” Miller said.
Frustrated by an inability to help SARDS patients in the past, Miller purchased the test but is waiting to offer treatment until “some of the details [are] worked out; [and] the pitfalls explored.” He will, however, refer clients to Iowa State for treatment.
Helpful Diagnostic Tool
Once Grozdanic realized that SARDS patients had different pupil light reflexes (PLR), he designed a test that allowed practitioners to differentiate the disease from other retinal issues. Grozdanic discovered that although SARDS patients have a strong PLR to blue light (480nm, 200 kcd/m2) that reflex is absent when red light of the same intensity is used.
Because dogs are unable to tell doctors when they lost – or began losing – their eyesight, veterinarians have been hard-pressed to separate SARDS from other diseases, without highly technical equipment. As a result, Miller believes that until recently SARDS has been a “catch-all term for a lot of retinopathies.”
Because SARDS worsens quickly, he hopes the new tool will lead to early intervention. Grozdanic had to disqualify three dogs from the experimental treatment because their retinal damage was too advanced. Such advancement occurs within months, he said.
“Presence of poor constriction or papillary escape with blue light is suggestive of advanced retinal degenerative changes, which cause irreversible reorganization of retinal elements,” he explained
Admitting that the test isn’t cheap, Miller said clients are thankful for the answers it provides. He has not experienced any pushback from pet owners, who get written diagnostic cost estimates.
“Somebody has to take the first step,” Miller said referring to his investment in the Melan-100 instrument, which retails for about $1,300. “I’ve always found that good medicine equals good economics.”
Experimental treatment given to two dogs – ages ten and eight – in April entailed four to five days of hospitalization with several rounds of IVIg infusions. A side effect noted was systemic hypertension that occurred during infusions, which were given over six-hour periods.
Two IVIg infusions were given twice (on day one and day three) in doses of 0.5 mg/kg per body weight. Grozdanic explained that IVIg is a mixture of different globulins found in healthy human circulation. He described the product as a mosaic of normal antibodies that prevent the immune system from attacking antigens regularly encountered by the body. Infusion costs, which vary, are currently at $75 per 100g, Grozdanic said.
The two dogs regained a percentage of functional vision and can avoid large objects. The dogs cannot track smaller objects, like tennis balls, but owners reported improvements in behavior and quality of life, Grozdanic said.
Because time is of the essence, Grozdanic encourages private practitioners to conduct regular eye exams and hone their ability to differentiate between problems in the retina, optic nerve, or brain, as well as identify signs of system disease other than blindness. All cases of sudden blindness should be referred to veterinary ophthalmologists as soon as possible, he added.