Sudden acquired retinal degeneration

Sudden acquired retinal degeneration (SARD) is a disease in dogs causing sudden blindness. It can occur in any breed, but female dogs may be predisposed. [cite journal |author=Cullen C, Grahn B |title=Diagnostic ophthalmology. Acute prechiasmal blindness due to sudden acquired retinal degeneration syndrome |journal=Can Vet J |volume=43 |issue=9 |pages=729–30 |year=2002 |pmid=12240536] Approximately 4000 cases are seen in the United States annually.cite journal | title = Some blind dogs may get chance to see again | journal = DVM | pages = 1S | publisher = Advanstar Communications | month = July | year = 2007 ]

The cause of SARD is considered to be idiopathic and the veterinary community is divided as to its cause, but the disease possibly involves autoimmune disease, toxins, Adrenal Exhaustion (also known as adrenal fatigue, hyperestrogenism, or atypical Cushings) [Levin C. Sudden Acquired Retinal Degeneration, associated pattern of adrenal activity, and hormone replacement in three dogs – a retrospective study. Proceedings of the 38th Annual Meeting of the College of Veterinary Ophthalmologists 2007; 38: 32.] [Levin C. (2008) Adrenal exhaustion and immunoglobulin suppression: common findings in 43 dogs with Sudden Acquired Retinal Degeneration (SARD) www.petcarebooks.com/research] or Cushing's disease.cite book|author=Gelatt, Kirk N. (ed.)|title=Veterinary Ophthalmology|edition=3rd ed.|publisher=Lippincott, Williams & Wilkins|year=1999|id=ISBN 0-683-30076-8] Symptoms include sudden permanent blindness, but may occur more slowly over several days, weeks or months, [cite web | title = Sudden Acquired Retinal Degeneration (SARD) | work = The Merck Veterinary Manual | year = 2006 | url = http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/160611.htm| accessdate = 2007-03-11 ] dilated pupils, and loss of the pupillary light reflex. Other symptoms commonly seen are similar to those seen with Cushing's disease or Adrenal Exhaustion and include increased water consumption and urination, weight gain, confusion, restlessness, behavioral changes and lethargy. Pets suffering from Adrenal Exhaustion differ in that they often exhibit chronic inflammation (mouth, gut, skin, etc.), caused by the inflammatory effect of high estrogen levels that accompany Adrenal Exhaustion. These symptoms may develop over a few months preceding the onset of SARD. [cite web | last = Ofri | first = Ron | title = Examination of the Blind Animal | work = Proceedings of the 31st World Congress of the World Small Animal Veterinary Association | year = 2006 | url = http://www.ivis.org/proceedings/wsava/2006/lecture21/Ofri2.pdf?LA=1 | accessdate = 2007-03-11 ] Despite similar symptoms and blood test results to Cushing's disease, evaluation of dogs with SARD did not reveal any tumors in the pituitary or adrenal glands. [cite journal |author=Gilmour M, Cardenas M, Blaik M, Bahr R, McGinnis J |title=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 |journal=Am J Vet Res |volume=67 |issue=5 |pages=877–81 |year=2006 |pmid=16649924 |doi=10.2460/ajvr.67.5.877] However, endocrine testing total cortisol and estrogen levels often show the pet suffering from Adrenal Exhaustion. Autoimmune disease as a cause has also been called into question because of a lack of antiretinal autoantibodies in dogs with SARD in one study. [cite journal |author=Keller R, Kania S, Hendrix D, Ward D, Abrams K |title=Evaluation of canine serum for the presence of antiretinal autoantibodies in sudden acquired retinal degeneration syndrome |journal=Vet Ophthalmol |volume=9 |issue=3 |pages=195–200 |year=2006 |pmid=16634935 |doi=10.1111/j.1463-5224.2006.00466.x]

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. [cite journal |author=Miller P, Galbreath E, Kehren J, Steinberg H, Dubielzig R |title=Photoreceptor cell death by apoptosis in dogs with sudden acquired retinal degeneration syndrome |journal=Am J Vet Res |volume=59 |issue=2 |pages=149–52 |year=1998 |pmid=9492927] SARD 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 SARD. [cite web | last = Gilger | first = Brian C. | title = Diagnosis and Treatment of Ocular Fundus Disorders of Geriatric Dogs | work = Proceedings of the North American Veterinary Conference | year = 2006 | url = http://www.ivis.org/proceedings/navc/2006/SAE/305.pdf?LA=1 | format = PDF | accessdate = 2007-03-11 ] Currently there is no approved treatment, although the use of intravenous immunoglobulin has been investigated due to similarities between SARD and human immune-mediated retinopathy. However, if endocrine testing reveals the pet as suffering from Adrenal Exhaustion, "thyroid and steroid replacement" therapy has been shown to be beneficial to the pet's overall health as well as maintaining vision in pets that are not yet totally blind. [Levin C, SARDS Case Report #2 Hormone replacement in a Beagle affected with Sudden Acquired Retinal Degeneration Syndrome (SARDS)(Oct. 2006)] [Levin C, SARDS case report #7 Reversal of blindness and elevated adrenal activityin a Springer Spaniel with Sudden Acquired Retinal Degeneration (Jan. 2008)]

References