Sudden acquired retinal degeneration syndrome explained

Sudden acquired retinal degeneration syndrome (SARDS) is a disease in dogs causing sudden blindness. It can occur in any breed, but female dogs may be predisposed.[1] Approximately 4000 cases are seen in the United States annually.[2]

Characteristics

Symptoms include sudden permanent blindness, but may occur more slowly over several days, weeks or months,[3] dilated pupils. Pupillary light reflexes are usually reduced but present; the slow phase mediated by melanopsin in retinal ganglion cells is retained. Other symptoms commonly seen are similar to those seen with Cushing's disease and include increased water consumption and urination, weight gain, confusion, restlessness, behavioral changes and lethargy. These symptoms may develop over a few months preceding the onset of SARDS.[4] Clinical signs and disease progression vary markedly among individual animals, depending on the number and type of hormones that are increased, the degree of hormone elevation, and the age of the dog.[5]

Some owners notice a more obvious "eye shine" in photographs due to the dilated pupils and retinal atrophy creating what is described as a "hyper-reflective tapetum".

Causes

The cause of SARDS is considered to be idiopathic and the veterinary community is divided as to its cause, but the most common hypotheses on the causes of the disease possibly include autoimmune disease, or exposure to toxins. Autoimmune disease as a cause is controversial because some studies have supported the presence of antiretinal autoantibodies in dogs with SARDS,[6] [7] but others have failed to show a link.[8] Despite similar symptoms and blood test results to Cushing's disease, evaluation of dogs with SARDS did not reveal any tumors in the pituitary or adrenal glands,[9] and recent work has indicated significant differences in the clinical and laboratory test parameters between the two diseases.[10]

Diagnosis

Examination with an ophthalmoscope will initially show no changes, but in a few months atrophy of the retina will resemble the appearance of progressive retinal atrophy. Pathologically, there is a loss of the rod and cone cells followed by degeneration of other layers of the retina. The retinal degeneration appears to be related to apoptosis of these cells.[11] SARDS must be distinguished from other causes of sudden blindness that have no visible pathology, including retrobulbar optic neuritis, a tumor at the optic chiasm, or other central nervous system diseases. Electroretinography is useful to definitively diagnose SARDS.[12]

Treatment

While there is no unilateral treatment for SARDS[13] researchers at the Iowa State University led by Dr. Siniša Grozdanić, ISU Veterinary Ophthalmologist have successfully restored vision in two dogs who have been in 2007 successfully treated through an experimental treatment by intravenous immunoglobin (IVIg). "Although the dogs won't be catching any Frisbees, they can navigate and not bump into objects,", Dr. Grozdanić notes.[14]

Various immunosuppressive treatment regimens have been tried, but are not consistently effective.[15] Treatment regimens with adrenal steroids and thyroid hormones have been proposed, but as of 2016 no controlled, peer reviewed studies had investigated the effectiveness of such treatments.

Notes and References

  1. Cullen C, Grahn B . DIAGNOSTIC OPHTHALMOLOGY: What are your clinical diagnosis, lesion localization, and differential diagnoses? . Can Vet J . 43 . 9 . 729–30 . 2002 . 12240536 . 339566.
  2. Some blind dogs may get chance to see again . DVM . 1S . Advanstar Communications . July 2007 .
  3. Web site: Sudden Acquired Retinal Degeneration (SARD) . The Merck Veterinary Manual . 2006 . 2007-03-11 .
  4. Web site: Ofri . Ron . Examination of the Blind Animal . Proceedings of the 31st World Congress of the World Small Animal Veterinary Association . 2006 . 2007-03-11 .
  5. Carter RT, Bentley E, Oliver JW, et al.: Elevations in adrenal sex hormones in canine sudden acquired retinal degeneration syndrome (SARDS) [abstract]. Proc Am Coll Vet Ophthalmol:9:40, 2003.
  6. Braus. Barbara K.. Hauck. Stefanie M.. Amann. Barbara. Heinrich. Christine. Fritsche. Jens. Köstlin. Roberto. Deeg. Cornelia A.. July 2008. Neuron-specific enolase antibodies in patients with sudden acquired retinal degeneration syndrome. Veterinary Immunology and Immunopathology. 124. 1–2. 177–183. 10.1016/j.vetimm.2008.02.020. 18405980.
  7. Bellhorn. R. W.. Murphy. C. J.. Thirkill. C. E.. February 1988. Anti-retinal immunoglobulins in canine ocular diseases. Seminars in Veterinary Medicine and Surgery (Small Animal). 3. 1. 28–32. 0882-0511. 3363244.
  8. Keller R, Kania S, Hendrix D, Ward D, Abrams K. 2006. Evaluation of canine serum for the presence of antiretinal autoantibodies in sudden acquired retinal degeneration syndrome. Veterinary Ophthalmology. 9. 3. 195–200. 10.1111/j.1463-5224.2006.00466.x. 16634935.
  9. Gilmour M, Cardenas M, Blaik M, Bahr R, McGinnis J . Evaluation of a comparative pathogenesis between cancer-associated retinopathy in humans and sudden acquired retinal degeneration syndrome in dogs via diagnostic imaging and western blot analysis . Am J Vet Res . 67 . 5 . 877–81 . 2006 . 16649924 . 10.2460/ajvr.67.5.877. free .
  10. Oh. Annie. Foster. Melanie L.. Williams. Jonathan G.. Zheng. Chaowen. Ru. Hongyu. Lunn. Katharine F.. Mowat. Freya M.. 2019-03-12. Diagnostic utility of clinical and laboratory test parameters for differentiating between sudden acquired retinal degeneration syndrome and pituitary-dependent hyperadrenocorticism in dogs. Veterinary Ophthalmology. 22 . 6 . 842–858 . 10.1111/vop.12661. 30864251. 76666023 .
  11. Miller P, Galbreath E, Kehren J, Steinberg H, Dubielzig R . Photoreceptor cell death by apoptosis in dogs with sudden acquired retinal degeneration syndrome . Am J Vet Res . 59 . 2 . 149–52 . 1998 . 9492927.
  12. Web site: Gilger . Brian C. . Diagnosis and Treatment of Ocular Fundus Disorders of Geriatric Dogs . Proceedings of the North American Veterinary Conference . 2006 . PDF . 2007-03-11 . dead . https://web.archive.org/web/20070929110028/http://www.ivis.org/proceedings/navc/2006/SAE/305.pdf?LA=1 . 2007-09-29 .
  13. Komáromy. AM. Abrams. KL. Heckenlively. JR. Lundy. SK. Maggs. DJ. Leeth. CM. MohanKumar. PS. Petersen-Jones. SM. Serreze. DV. van der Woerdt. A. Sudden acquired retinal degeneration syndrome (SARDS) - a review and proposed strategies toward a better understanding of pathogenesis, early diagnosis, and therapy.. Veterinary Ophthalmology. July 2016. 19. 4. 319–31. 10.1111/vop.12291. 26096588. 2027.42/122446. free.
  14. Web site: Blind dogs can see after new ISU treatment for a sudden onset blinding disease • News Service • Iowa State University. 2021-09-15. www.news.iastate.edu.
  15. Young. Whitney M.. Oh. Annie. Williams. Jonathan G.. Foster. Melanie L.. Miller. William W.. Lunn. Katharine F.. Mowat. Freya M.. November 2018. Clinical therapeutic efficacy of mycophenolate mofetil in the treatment of SARDS in dogs-a prospective open-label pilot study. Veterinary Ophthalmology. 21. 6. 565–576. 10.1111/vop.12545. 29383824. 23927483 . free.

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