Losing your vision can be a life-altering event. The same is true for our dogs. There are several causes of blindness in dogs—one of those causes is sudden acquired retinal degeneration syndrome (SARDS).
SARDS is characterized by the sudden and rapid destruction of photoreceptors in the retina. The retina is located at the back of the eye. Photoreceptors in the retina capture light that enters the eye and convert the light into electrical signals. These signals are sent to the brain through the optic nerve. The brain converts these electrical signals into an image of what your dog sees.
There are two types of photoreceptors in the retina—rods and cones. Rods are responsible for detecting the level of light (or brightness) and motion. Cones are responsible for detecting color. Unlike humans, dogs only have two types of cones and can perceive the colors blue and yellow but not red and green.
Destruction of the photoreceptors occurs over a period of a few weeks, although most dogs with SARDS seem to become completely blind overnight. Symptoms of SARDS include bumping into furniture and walls and having dilated pupils. Some dogs will become anxious and withdrawn or may whine and appear restless.
Causes of SARDS
The cause of SARDS is unknown. There are no known toxins that cause SARDS. There is speculation that the development of SARDS may be linked to an underlying endocrine disorder, such as hyperadrenocorticism (Cushing’s disease) or hypothyroidism. This link has not been confirmed but is currently being researched.
Diagnosing SARDS in Dogs
Proper diagnosis of SARDS in your dog will require a visit to a veterinary ophthalmologist. Your dog will receive a complete ophthalmologic exam, including an electroretinogram (ERG). An ERG records the electrical activity of the retina when exposed to light. Dogs with SARDS will have no retinal electrical activity due to the destruction of photoreceptors in the retina.
The ERG takes about 20 to 30 minutes to complete. Your dog is first placed in a completely dark room for about 15 minutes. This immersion into darkness makes the retina particularly sensitive to light.
The pupils will need to be dilated for this test. If your dog’s pupils are not already dilated, a drop of a pupil dilation solution (such as tropicamide ophthalmic solution) will be instilled in each eye. Then a drop of a cornea numbing solution (such as proparacaine or tetracaine) is applied to the surface of each eye. This numbs the surface of the cornea in preparation for the ERG.
A contact lens that contains an electrode is applied to the surface of your dog’s cornea. Two electrodes are applied to your dog’s skin. One electrode is placed at the top of his skull and the other is placed next to the eye being tested.
Pulses of light are shone into the eye being tested. Electrical activity of the retina is recorded by the electrodes and the output is displayed on a computer. Lack of retinal electrical activity confirms the diagnosis of SARDS.
Your dog needs to sit still without moving his head during the ERG. Most dogs will require a sedative for the procedure. Some dogs may need to be briefly anesthetized to facilitate completion of the ERG.
Treatment and Prognosis for Dogs with SARDS
There are currently no treatments for SARDS. Blindness is permanent and irreversible. SARDS is not a painful condition. Most dogs will adjust to being visually impaired and lead a full and happy life.
If you suspect that your dog has become acutely blind, make an appointment for an exam with his primary care veterinarian immediately. She can complete some basic diagnostic tests of his eyes and determine if your dog needs to be referred to a veterinary ophthalmologist for further workup of his vision loss.
Much like people who have acutely lost their vision, dogs with SARDS need help learning how to navigate their environment without their sight. Here are some things you can do to help your visually impaired dog:
- Keep furniture and other obstacles in their current locations. Dogs will create a mental map of their environment to help them navigate without vision. If you must move furniture or other fixed items, do it gradually to minimize disruption of your dog’s mental map. This will help your dog adjust to the new location of the moved items.
- Block access to stairs with safety gates.
- Place a throw rug over the threshold or at the entrance to a room. Use a different rug texture for each room so that your dog can detect by touch the room he is entering or exiting.
- Use different landscape textures in your yard—such as grass, landscape pavers, pebbles, or sand—to indicate transitioning between yard sections and proximity to an exterior door of your home.
- Put away loose or unstable items that may create trip or fall hazards in your home.
- Teach your dog navigation terms, such as “right”, “left”, and “step”.
- Walk your dog on a leash when outside in the yard until he has become familiar with how to navigate the yard.
Devices that can help your visually impaired dog:
- Goggles can protect your dog’s eyes from trauma that might be incurred by walking into bushes or tall brush. Rex Specs has created an excellent pair of goggles made specifically for dogs—see Whole Dog Journal’s 2023 Dog Gear of the Year for more information.
- Wearing a navigation halo from Muffin’s Halo can help dogs realize they are about to bump into an object BEFORE it happens. See https://www.muffinshalo.com/ for more information.
