Once the primary care DVM believes the diabetes is relatively well-controlled and the owner is determined to be interested in possibly pursuing cataract surgery, a comprehensive ophthalmic examination/consultation via an ophthalmologist is warranted. Diabetes induced cataracts can develop remarkably quickly and can cause a complete loss of vision in less than 48 hours.Īs blood glucose levels increase, glucose also increases within the aqueous humor, glucose readily diffuses across the lens capsule, an aldose reductase pathway converts glucose to sorbitol, sorbitol accumulates within the lens as it cannot diffuse through lens cell membranes, the osmotic gradient increases, water enters the lens and irreversibly changes the lens structure via lens fiber swelling and rupture, vacuole formation, and clinically evident cataract. The majority of dogs with diabetes mellitus will develop cataracts within 5-6 months from the time of diagnosis of the disease. Diabetes Mellitus Induced Mature Cataract It may take 2 to 4 weeks for the retinas to reattach, most vision returns, the fundus ultimately illustrates minimal scarring, and the immunosuppressive therapy is very slowly tapered, and in most cases, eventually stopped altogether. If ancillary diagnostic tests rule out infectious disease or other systemic causes, corticosteroids and/or other nonsteroidal immunosuppressive medication are begun e.g., mycophenolate mofetil (Cellcept) which can be combined with prednisone, is inexpensive, has minimal side effects, and is typically given at 10mg/kg PO BID and, azathioprine (Imuran) which also can be combined with prednisone, is moderately expensive, can have significant hepatotoxicity and bone marrow suppression, and is typically begun at 2 mg/kg PO daily and tapered. Following the comprehensive ophthalmic examination, a physical examination is performed, a blood pressure is obtained, and a comprehensive blood profile is submitted. Affected dogs present with a bilateral, nonrhegmatogenous, serous, bullous retinal detachment which may involve all or most of the fundus. Immune-mediated retinal detachment syndrome typically affects middle-aged and older dogs, is nonpainful, of rapid onset, and eliminates most or all of the functional vision. Immune-Mediated Retinal Detachment Syndrome In a recent peer-reviewed journal article involving 100 dogs with SARD, owners generally perceived that dogs with SARD have moderate to excellent quality of life and most owners (95%) discouraged euthanasia for dogs with SARD. As a result, owners are informed their dog with be handicapped thereafter but can still enjoy a high quality of life nonetheless. There is no validated medical or surgical treatment available for SARD. A neurologic consultation is then recommended and a CSF analysis and MRI of the skull may be pursued. If, on the other hand, the ERG yields normal electrical responses for both eyes, then the loss of vision is considered central i.e., bilateral optic neuritis, an optic chiasmal lesion at the base of the brain, or an optic tract and/or visual occipital cortex based problem. An absent or extinguished ERG response supports the diagnosis of SARD. A light is flashed at the eye and the electrical response is amplified and recorded on a computer. Tropicamide is instilled, the patient is dark adapted, topical proparacaine is instilled, a ground stick pin electrode is inserted within the skin of the forehead, a reference stick pin electrode is inserted adjacent to the lateral canthus, and a gold leaf electrode embedded within a contact lens is placed on the cornea after applying a methylcellulose gel. The ERG is a nonpainful electrophysiologic test. The electroretinogram (ERG) represents a summation of electrical potentials originating from the rod and cone photoreceptors and is necessary for definitively ruling in or ruling out SARD. Laboratory abnormalities consistent with hyperadrenocorticism are common although definitive biochemical proof of the disease is often lacking in dogs with SARD. Middle aged to older dogs are affected and occasionally Cushing’s-like clinical signs (polyphagia, weight gain, polyuria, and polydipsia) develop in conjunction with SARD. ![]() Affected dogs present with dilated and nonresponsive or poorly responsive pupils, fail a maze test under well- and dimly-lighted conditions, and have an ophthalmoscopically normal fundus. Dachshunds, Miniature Schnauzers and females are overrepresented. SARD is nonpainful and idiopathic but possibly immune-mediated. Sudden acquired retinal degeneration (SARD) is characterized by a sudden (< 1 month), usually total, permanent blindness in an otherwise healthy dog. Steve Dugan, DVM, MS, Diplomate of the ACVO Sudden Acquired Retinal Degeneration (SARD) Sudden Acquired Retinal Degeneration (SARD), Immune-Mediated Retinal Detachment Syndrome and Diabetes Mellitus Induced Mature Cataract are common causes of blindness in dogs.
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