SARDS is a condition that causes blindness in dogs which occurs suddenly and has no other visible disease of the eye or retina. SARDS is however associated with other abnormal metabolic signs such as increased drinking of water, increased urination, increased appetite, and weight gain. Laboratory values may also be abnormal with low lymphocyte counts, high neutrophil counts and elevation of alkaline phosphatase. The ACTH stimulation test for Cushing’s disease is often positive.
SARDS has been recognized in dogs for over 2 decades. While the cause remains unknown, there are studies that have indicated that increased antibodies to the retina are found in the eye as well as increased levels of complement activity. Complement activity is associated with increased immune damage.
The syndrome tends to occur in older spayed females of both pure breed and mixed breeds with a predisposition to Dachshunds, Pugs, Miniature Schnauzers and Brittany Spaniels. There is also a seasonal incidence with 46% of the cases occurring in December and January.
The disease causes death of the rods and cones in the retina. This loss of cells eventually will cause visible retinal thinning, but this is later in the course of the disease. Electroretinogram (ERG) is the gold standard for diagnosis the loss of the retinal cells, but this test is difficult to have done.
Recently it has been noted that the pupillary light reflexes (PLR) differ with different frequencies (colors) of light. For example, blue light of 480nm wavelength and red light of 630nm wavelength stimulate different pathways of the PLR. A pet with a normal retina would respond (constrict) to both colors of light. Dogs that have SARDS have complete pupillary constriction (normal PLR) in response to blue light of 480nm and no PLR to red light at 630nm. The response to blue light is due to the stimulation of melanopsin. Melanopsin is a photosensitive pigment located in retinal ganglion cells. When stimulated it will drive the PLR. When red light of 630nm is used on normal pets the rods and cones of the retina stimulate the PLR. In SARDS patients with red light, the pupils remain fixed and dilated. Red light does not activate the melanopsin pathway for pupillary light reflexes but does activate the rods and the cones in a normal retina. SARDS pets have no rod or cone activity in their retina.
SARDS, until recently, has been considered an untreatable, irreversible blinding disease of dogs. Recently however the experimental use of human immunoglobulin therapy (IVIg) has resulted in restoration of limited visual behavior in some SARDS-affected dogs if given early in the course of the disease. It is this result that indicates the possibility that Stem Cell Therapy given intravenously would be a more effective therapy.
Immune-Mediated Retinitis (IMR)
IMR is a potentially blinding disease of dogs like SARDS in clinical presentation. IMR may start as night blindness or may present with sudden complete blindness. The owner may report previous episodes of sporadic or temporary blindness or decreased vision months or years before the development of complete blindness. Commonly, the pet will have large, dilated pupils even in bright light. Unlike SARDS the pet will not show any of the other health issues. Visual evaluation of the retina is normal. There is complete loss of the pupillary light reflex when red light is used and a normal response when blue light is used. ERG activity may be normal, supernormal or decreased whereas SARDS pets have extinguished ERG responses. One eye ERG results may be different from the opposite eye. In human’s cancer associated retinal disease (CAR) is similar in pathological appearance to IMR and 20% of the pets diagnosed with IMR are found to have cancer or other serious abnormalities. Pets with IMR can be treated with immunosuppressive therapy and doxycycline. Therapy will usually cure blindness within 1 to 2 days but must be continued and the dose over time may have to be increased to maintain vision.
Menace reflex rarely returns.
Immune mediated disease of the retina such as SARDS and IMR result from an imbalance in the immune system. When the immune system attacks normal tissues, it is due to the lack of immune tolerance. Tolerance to normal tissues is mediated or regulated by T-lymphocytes called Treg cells. Treg cells are increased by the presence of stem cells. Stem cell therapy reduces inflammation, increases Treg cells and produces long lived tolerance to normal tissues. SARDS and IMR are diseases that should respond very well to stem cell therapy but there have been so few cases that it is difficult to say this for certain. Therefore we are starting a clinical trial to test this premise.
Criteria for Stem Cell Therapy for SARDS and IMR
We are conducting our own evaluation of the effectiveness of stem cell therapy for the treatment of these immune mediated diseases of the eye. We are happy to send stem cells to local veterinarians for intravenous administration. The cost for these cells will be $500.
- Pets must be in good health. We do not treat animals with hypertension, kidney disease or liver disease. If a heart murmur is detected, the pet must be evaluated with ultrasound, EKG and found to be within normal limits of cardiac output prior to the therapy.
- Pets that have cataracts or glaucoma (even if treated) should not be treated as pre-existing ocular disease may affect the stem cell therapy.
- Dogs should be examined by an ophthalmologist to determine retinal status. If there are signs of hyperreflectivity on fundus examination, should not be treated.
- Animals that have been blind for more than 6 months should not be treated. Animals should be treated within 2 months of blindness for best results.
- As soon as the pet is diagnosed with blindness the pet should be treated as if the diagnosis is IMR. (High dose steroids and doxycycline). This should be done until stem cell therapy can be arranged.