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Even if you have never considered adopting a blind pet, that doesn't mean you are immune from sharing your life with a blind pet. Acute blindness is an adjustment for both pets and pet parents. Hopefully this will never happen to you or your beloved fur kid, but reading up on this cause of sudden blindness would behoove you so you don't find yourself in the dark should this happen to you.
Sudden acquired retinal degeneration (SARDS) is an acute loss of function of the entire retina of both eyes that results in blindness. Other names for the condition are Silent Retina Syndrome, Neurotoxic Retinopathy, and Metabolic Toxic Retinopathy.
Is your dog at risk?
SARDS occurs only in dogs and affects primarily adult, large-breed dogs. Dachshunds and Miniature Schnauzers are small breeds that are predisposed to SARDS but the condition may strike any pure or mixed breed dog. SARDS is reported to occur most commonly in dogs 6 to 14 years of age and it seems female dogs may be predisposed.
How sudden is SARDS?
Affected dogs often have a history of rapid vision loss occurring over periods of 24 hours to one month. Most dogs will go completely blind within four weeks of the noticeable onset of vision loss, and many dogs will have total vision loss within one to two weeks.
What causes SARDS?
Although several theories have been proposed, the cause of SARDS is unknown. For some reason, the cells that detect light in the retina, called photoreceptors, stop functioning. Both types of photoreceptors (rods and cones) are affected. After the photoreceptors stop functioning, the retina slowly degenerates. It is thought to be caused by the release of a steroid-like substance from the dog’s own body that is toxic to the retina and slightly toxic to the liver. SARDS is not currently believed to be an inherited condition.
What would a pet parent of a dog suffering from SARDS typically notice?
Affected dogs start bumping into objects regardless of lighting level and often act very disoriented. Some dogs become afraid and are easily startled, which may result in perceived temperament changes. Looking closely at the eyes, you may find both pupils are usually dilated and do not respond well to light. Affected dogs may blink their eyes less often, stare into space, and have mild eye redness and tearing.
Oddly enough, at about the time that vision changes are noticeable, many pet parents notice their dogs develop increased thirst and appetite. In many cases, the dog will also gain weight.
Diagnosis of SARDS
This combination of increased thirst and hunger along with vision signs is often enough to cause your veterinarian to suspect SARDS. A thorough eye examination must be performed to rule out glaucoma, retinal detachments, and intraocular inflammation as the cause of blindness. Early in the course of the disease, the retina usually appears normal or may show subtle changes in the blood vessels.
An accurate diagnosis of SARDS involves a thorough blood and urine profile, blood pressure readings, and a test of retinal function known as an electroretinogram (ERG), which usually must be performed by a veterinary ophthalmologist. Laboratory tests may also be performed for hyperadrenocorticism, a more common cause of increased thirst, urination, and appetite. Sometimes the lab work may cause a veterinarian to believe the patient is suffering from hyperadrenocorticism, but treatment for this disease will not restore vision. The relationship between hyperadrenocorticism and SARDS is not understood.
Because the retina appears normal upon initial evaluation, the ERG is crucial because it distinguishes SARDS from other common causes of blindness, including central nervous system disorders of the optic nerve or the brain. SARDS is peculiar in that the retina can look relatively normal yet there is significant retinal damage present.
The sad news is that there is no scientifically proven treatment for SARDS; most dogs are irreversibly blind. It’s not all bad news though; this disease is not painful to dogs. As far as different causes of blindness in dogs, this is a good diagnosis to receive. Unlike with a diagnosis of central blindness, there will likely be no widespread or serious internal problems for your dog.
As far as coping, it seems we have much to learn from our canine companions. Most dogs typically do remarkably well adjusting to life without vision. After an initial adjustment period of about 6 weeks, most dogs are able to rely on their senses of smell and hearing to return to almost normal activity levels and interactions with other animals and family members. With all blind pets, it is important to keep the home environment as stable as possible and objects should be kept in consistent locations. Pets should not be left outside unattended unless they are in a confined space such as a yard.