Blindness in Older Dogs
As our pets age their sight begins to diminish, most of the time it is due to just getting older and cataracts slowly develop. You might notice that they don’t see things that would normally catch their attention. My dog no longer sees the squirrel taunting her from the bird bath, which at one point in her life would send her tearing across the lawn in hot pursuit. Other more serious causes can come on suddenly and you will notice an abrupt change in their behavior like bumping into things that they would normally be able to navigate around. Dogs can become far sighted like us but it rarely causes blindness
Cataracts have a genetic basis and are often breed and age specific. They can occur at any age but usually occur later in life and develop gradually. Some signs to watch for are a progressive whitening of the lens, clumsy behavior, bumping into things, reluctance to move, and acting worse in dim light. Most cataracts can be surgically removed by a veterinary ophthalmologist and your pet will be able to see again.
Cataracts that come on suddenly are commonly associated with diabetes. You need to have your veterinarian draw blood and check their sugar level to determine if diabetes is a concern. Cataracts do not develop in diabetic cats.
Glaucoma and uveitis (inflammation inside the eye) can cause blindness and are usually very painful. You might observe redness, swelling, or changes in the appearance of the eye. They can occur in one or both eyes. These conditions can be treated depending on the cause but sometimes can result in permanent loss of vision.
The back of the eye is called the retina, if the retina is injured or has a disease it can cause blindness. SARDS (sudden acquired retinal degeneration) is a disease that affects older dogs. The onset is quick, no one really knows what causes it, and there is no treatment. Other diseases of the retina include retinal detachment or damage from an accidental overdose of ivermectin (the ingredient found in most heartworm preventions).
The optic nerve is the next place that can cause blindness. They can get a tumor on the nerve which will cause loss of vision. This type of blindness is usually in one eye so you might only notice vision loss on one side. Lead toxicity can also cause damage to the optic nerve and cause blindness. This type of toxicity usually damages both eyes.
If injury occurs somewhere on the pathway from the optic nerve up to the brain and back to the eye blindness can occur. In an older dog a brain tumor would be the most likely cause.
The good news about blindness in animals is that most adapt to their condition much better than people, they do not have the emotions like we do to cause problems. Their other senses are enhanced so they use their sense of smell, hearing, and touch to get around. Keeping their environment as constant as possible also helps them move around better; don’t rearrange the furniture, unclutter the floor where they walk, and put up barriers so they can’t fall down the stairs or off something high like a landing or deck outside.
Some situations to be extra careful in are negotiating the stairs, being in an unfamiliar or busy environment, meeting other dogs, meeting children, or moving to a new home. Using a harness at first or using treats to make a scent trail may help them to initially navigate their environment better. Some dogs that are very dominant or very nervous may become more aggressive and potentially dangerous when blind. Training and medications can help in some instances. Blindness is an adjustment but most of the time can be managed with a little work and patients.
M. H. Archer, DVM