Dog Blindness: Sudden Acquired Retinal Degeneration and Immune-Mediated Retinopathy

Sudden Acquired Retinal Degeneration Syndrome (SARDS - toxic neuroretinopathy, metabolic toxic retinopathy and silent retina syndrome 1) cause blindness among most breed of healthy dogs, usually affects smaller breeds (Miniature Schnauzers, Dachshunds, and Brittany Spaniels). "In an eye that has been affected, the visual layer (comprised of the rods and cones) is completely destroyed". Onset of visual loss generally strikes dogs between the age of seven and fourteen years old and predominately affects more females (70% 2 ) than males. The onset of SARDS occurs from a few hours or days to a week or two, leading up to blindness. During this time of increase loss of vision, dogs exhibit dramatic increase appetite and water consumption, probably related to increase hormones (cortisol levels).2 Also, canines exhibit frequent urination. 7 The symptoms of SARDS may be suggestive of Cushing Syndrome, treatable but will not restore vision. 2 In 1980's, Sudden Acquired Retinal Degeneration identified: Dogs retinas showed no electrical activity. Approximately 4,000 dogs each year in United States diagnosed with SARDS. 5 Sudden Acquired Retinal Degeneration is not an inherited or genetic disorder. 7

Caroline D. Levin, registered ophthalmologic nurse theorizes, possible cause of SARDS related to insufficient nutrition from some commercial pet foods (describe by Dr. Levin) might cause intestinal damage that triggers a destructive response in the cellular network. 3 Confirming or disapproving diagnosis of SARD's includes blood and urine test, blood pressure measurement and electroretinogram (ERG - test of retinal function). If ERG report retina is working normally, then the blindness is not related to SARDS. "If the ERG is flat (Indication of outer retinal damage 8) and the blood pressure is normal, then SARDS is the most likely diagnosis." 4 Also, optical coherence tomography scan diagnosis SARDS (In April 2007, only Iowa State University Veterinary Medicine Hospital has this advance diagnostic technology, more commonly found human ophthalmology centers.5). 4 Also Sudden Acquired Retinal Degeneration, initially cause canine sense of smell and hearing to diminish, but other senses eventually sharpen. 8 Unfortunately for many canines and their pet owners for a long period of time no treatment option available for Sudden Acquired Retinal Degeneration. 4

In April 2007, research team led by Iowa State University veterinary ophthalmologist Dr, Sinisa Grozdanic in the College of Veterinary Medicine restored vision of two dogs (April 12, and April 27) diagnosed with SARDS."The dogs were treated with intravenous immunoglobulin (IVIg), a human blood product that contains antibodies from the plasma of thousands of blood donors. It is used to treat immune deficiencies, inflammatory diseases and autoimmune diseases." However according to Dr. Grozdanic, immunoglobulin (IVIg) is not a good treatment for SARDS dogs have cardiac or kidney disease. Also, the potency of the medication not as effective for canines, have SARDS longer than two months. Early diagnosis of SARDS is vitally imperative for best treatment results. Estimated cost for treatment, hospitalization, and intensive care $1,200 and cost immunoglobulin (IVIg) between $35 - 40 per pound of the dog's body weight. Duration of treatment for SARDS varies few weeks to a few years according to Dr. Grozdanic. 5

In March 2008, published in Veterinary Clinics of North America Small Animal Practice edition, assistant professor Sinisa Grozdanic identified a new canine eye disease named Immune-Mediated Retinopathy (IMR - not previously named) similar to Sudden Acquired Retinal Degeneration. "Both diseases occur when the dog produces auto antibodies that attack the retinal cells. The antibodies mistake retinal cells for cancerous tumors or tissues that need to be destroyed." As result of the retinal cells being attacked, dog's vision is reduced or lost. Dr. Grozdanic discovered Immune-Mediated Retinopathy occurs as result of auto antibodies produced elsewhere in the dog (not in the eye), travels through the blood into the eyes. Dr Grozdanic surmise previous cases of SARDs may be identified as Immune-Mediated Retinopathy, treated differently. Distinguishing the difference between SARDS and IMR, Dr. Grozdanic developed a colored light test: When a dog's pupils constrict poorly to red light shine and normally constricts when blue light is used, likely diagnosis Immune-Mediated Retinopathy. "If the eyes respond to blue lights, but not red lights, then the diagnosis is SARDS". Dr. Grozdanic said: "In approximately 60 percent of the Immune-Mediated Retinopathy cases, we have been able to treat. In some cases very successfully, in some cases moderately successfully." Also Dr. Grozdanic theorizes, since Sudden Acquired Retinal Degeneration and Immune-Mediated Retinopathy similar to human diseases, a cure may be discovered in the farseable future. 6

References:

1.) SUDDEN AQUIRED RETINAL DEGENERATION (SARD'S) - http://www.acvo.org/public/sard.htm

2.) S.A.R.D.S. - http://www.myspecialdog.com/SARDS.aspx

3.) Elusive Diagnosis and SARDS - http://www.westiefoundation.org/newsletter/04sards.htm

4.) Sudden Acquired Retinal Degeneration (SARDS) - http://www.eyevet.info/sards.html

5.) Researchers find cure for dogs with sudden acquired retinal degeneration syndrome - http://www.news-medical.net/?id=25836

6.) Eye Disease in Canines Identified; Potential For Human Treatment - http://www.medicalnewstoday.com/articles/99515.php

7.) Sudden Acquired Degeneration Syndrome (SARDS) - http://www.michvet.com/library/ophthalmology_SARDS.asp

8.) SARDS (Sudden Acquired Retinal Degeneration Syndrome) - http://www.bichonhealth.org/HealthInfo/SARDS.asp