What is SARDs? – Sudden Acquired Retinal Degeneration Syndrome (SARDS) is a syndrome, which is characterized by a sudden onset of blindness in dogs. Approximately 50% of SARDS patients can have signs of the excessive appetite, excessive drinking and urination, and weight gain. SARDS usually develops in middle-aged dogs (predominantly in small and middle size breeds), and many of SARDS patients have a current or previous history of different auto-immune diseases. Clinical evidence and molecular data confirmed complex immunological mechanisms of retinal damage involving T-cells, macrophages, B-cells, activation of the retinal pigment epithelium, retinal auto-antibody production and complement activation confirming that SARDS is an immune-mediated disease, and not the disease of the unknown etiology. SARDS is not associated with the cancer. For more detailed information on clinical changes in SARDS and molecular mechanisms of SARDS you can read our peer reviewed article from the journal Veterinary Ophthalmology (published in 2018), which is available online for free:
www_ncbi_nlm_nih_gov_pubmed_30109754.pdf
onlinelibrary_wiley_com_doi_epdf_10_1111_vop_12597
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What is IMR? – Immune Mediated Retinitis (IMR) is a disease which is in many aspects very similar or almost identical to SARDS. Approximately 5% of IMR dogs may have an underlying cancer disease. Cancer presence may result in the excessive immune system activation with a goal of destroying the cancer, and in some cases the immune system will recognize identical molecules in the cancer cells and retinal cells, resulting in the misguided immune attack on the eye resulting in the vision loss and ultimately blindness (cancer-associated retinopathy - CAR).
For more detailed information on the cancer-associated retinopathy you can review our presentation from the Annual AmericanCollege of Veterinary Ophthalmology Conference in 2016
Proposed molecular mechanism of retinal damage in SARDS and IMR involves activation of T-cells, macrophages and B-cells. Auto-antibodies may come to attack the retina from the systemic circulation, but may be also produced locally in the ocular tissues resulting in negative serology tests (image is adopted from the Grozdanic et al, Antibody-mediated retinopathies in canine patients: mechanism, diagnosis and treatment modalities. Vet Clin North Am Small Anim Pract. 2008 Mar;38(2):361-87 Review
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Are SARDs and IMR dangerous for the general health of my pet? – SARDs and IMR are autoimmune diseases, which can frequently cause kidney damage (proteinuria, microalbuminuria, membranous glomerulonephritis), pancreatitis, low level of thyroid hormones (hypothyroidism), liver function abnormalities (elevation of liver enzymes, increased sensitivity to systemic steroid therapy), high blood pressure (systemic hypertension), pseudo-Cushing’s disease symptoms (excessive thirst and urination, excessive appetite and weight gain) and neurological symptoms (loss of vision, hearing, smell sensation, ataxia, depression, lethargy, change in mentation). These changes can be dangerous to the overall health of affected dogs. A detailed evaluation of the systemic organ status is highly recommended for these patients, even if no therapy for the possible vision restoration is planned.
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Are SARDs and IMR treatable diseases? – Over the last 10 years, our team had developed a completely novel diagnostic and treatment protocols for these diseases. We usually pursue systemic immunosuppressive therapy in combination with the systemic or intraocular intravenous immunoglobulin (IVIg) treatment with a goal of restoring some vision. In many patients, additional medical therapy is recommended to address possible abnormalities associated with function of different organs (kidneys, liver, endocrine glands, brain, etc.). We give the maximum effort to carefully tailor medical treatment for each patient with a goal of minimizing any possible side effects, and maximally increasing the chance for the successful treatment outcome. Based on our data, the most frequent cause of death in SARDS patients are pancreatitis, kidney failure and uncontrolled immune-mediated diseases affecting the gut, liver, brain and spinal cord. Similar causes of death are observed in IMR patients, however the patients with the history of the cancer, usually die as a result of the cancer progression.
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What is the success rate for the SARDs and IMR treatment?
Early SARDs and IMR: Dogs with early symptoms of SARDs and IMR usually have near normal or normal day vision, permanent or intermittent night vision deficits, depth perception issues (reluctance to walk up and down the stairs or jump on and off the bed, usually in dim light conditions), inability to see small treats, abnormal chromatic pupil light reflex responses, and decreased but still present ERG responses. Frequently these patients will have a history of the abnormal weight gain, excessive appetite, excessive thirst and urination, and history of elevated liver enzymes or presence of protein in the urine. These patients have 90-95% therapeutic success rate in terms of the long-term vision preservation when treated with immunosuppressive medications. The key for the successful treatment is early diagnosis. Please, visit your local ophthalmologist for a detailed ophthalmology evaluation as soon as you detect any of the above mentioned problems.
Intermediate SARDs: Dogs with intermediate SARDS usually have near normal or normal day vision, have complete night blindness, have abnormal chromatic pupil light reflex responses, and completely extinguished ERG responses "flat ERG". Frequently these patients will have a history of the abnormal weight gain, excessive appetite, excessive thirst and urination, and history of elevated liver enzymes or presence of protein in the urine. These patients have 85-90% therapeutic success rate in terms of the long-term vision preservation when treated with immunosuppressive medications. The key for the successful treatment is early diagnosis. All dogs with intermediate SARDS develop complete blindness unless treated. Please, visit your local ophthalmologist for a detailed ophthalmology evaluation as soon as you detect any of the above mentioned problems.
For more detailed information on the intermediate SARDS you can review our presentation from the Annual American College of Veterinary Ophthalmology Conference in 2016:
Advanced SARDs and IMR: These dogs are characterized with a complete day and night vision loss, have abnormal chromatic pupil light reflex responses, and completely extinguished ERG responses ("flat ERG"). Frequently these patients will have a history of the abnormal weight gain, excessive appetite, excessive thirst and urination, and history of elevated liver enzymes or presence of protein in the urine. These patients have 65% therapeutic success rate in terms of recovering visual navigation skills in bright light conditions, 30% success rate in terms of recovering menace response (hand motion detection) and 20% success rate in terms of tracking small objects in the visual field when treated with immunosuppressive medications in a timely manner. For more detailed information on the diagnosis, clinical findings and molecular mechanism of advanced SARDS you can view our conference presentation (ACVO 2022) and read our peer reviewed articles which are published online:
IOVS 2007 Grozdanic.pdf
Veterinary Ophthalmology - 2018 - Grozdanic - Optical coherence tomography and molecular analysis of sudden acquired.pdf
Veterinary Ophthalmology - 2021 - Grozdanic - Presumed cancer‐associated retinopathy CAR mimicking Sudden Acquired.pdf
Chronic advanced SARDs and IMR : Dogs with very advanced SARDs and IMR (blindness in a duration of more than 3 months, advanced retinal degenerative changes characterized by diffuse tapetal hyper-reflectivity) usually do not respond well to medical therapy for the vision restoration. However, many of these patients may have other systemic organ problems, and these problems should be properly addressed to secure the long-term health of these patients.
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What diagnostic tests are usually performed before pursuing potential treatment for SARDs and IMR?
We usually recommend following tests to be performed in each SARDs/IMR patient:
- Complete cell blood count
- Serum chemistry (including T4 and cPL-pancreatitis test)
- Urine analysis (including urine microalbumin levels)
- Blood pressure evaluation
- Thoracic and abdominal radiographs
- General and ophthalmology examination
- Visual maze testing in dim and bright light conditions
- Chromatic pupil light reflex testing and electroretinography (ERG) testing
For more information on SARDs and IMR please click here.
