By Dr. Becker
Blindness is partial or total loss of vision that can be present from birth, occur suddenly as a result of an injury or illness, or come on gradually as a pet ages due to diseases such as cataracts, glaucoma, or retinal degeneration.
Dogs and cats of any breed and any age can become blind, but it's more commonly seen in elderly pets.
Causes of Blindness
In addition to congenital (from birth) blindness and gradual age-related blindness, there are several medical conditions of the eye that can ultimately lead to blindness in pets.
- Progressive retinal atrophy (PRA) is an inherited disease that causes dogs, and to a much lesser extent kitties, to lose their eyesight over a period of months to years. PRA is most often seen in Cocker Spaniels, Border Collies, Irish Setters, Norwegian Elkhounds, Schnauzers, Poodles, and in Bengal, Abyssinian, and Persian cats.
The retina, which is in the back of the eye, is composed of rods that perceive light and cones that perceive color. Normally the rods and cones mature by the time an animal reaches about 12 weeks of age, but in some pets with PRA, they never completely mature and may begin to degenerate at an early age.
- Sudden acquired retinal degeneration syndrome (SARDS) generally strikes dogs between 7 and 14 years of age and is more common in females. The syndrome causes total destruction of the rods and cones of the retina. The typical onset of SARDS is sudden – sometimes it happens literally overnight. There's often a dramatic increase in a dog's thirst and appetite in the weeks before blindness occurs.
- Taurine deficiency in cats can cause progressive retinal degeneration that often goes unnoticed until the condition is quite advanced. The damage to the rods and cones of the retina and the underlying tapetum lucidum cannot be reversed by taurine supplementation. This is one reason I often discuss the importance of a balanced, species-appropriate diet for cats that includes natural dietary sources of taurine like fresh meat.
- In an autoimmune disease called uveodermatologic syndrome, a dog's body attacks its own melanocytes, which are the cells that produce pigment primarily in the skin, the retina, and the uveal tract of the eye. Usually, the first ocular sign pointing to uveodermatologic syndrome is uveitis, which ultimately leads to blindness.
- Diabetes mellitus can cause blindness in dogs, and rarely, in cats.
- Other potential causes of blindness in both dogs and cats include untreated eye infections, inflammation of the eye, glaucoma, cataracts, dry eye syndrome, infectious disease, trauma to the eye, high blood pressure secondary to another disease, stroke, cancer or another type of tumor located in the eye or brain, and a drug reaction.
Symptoms and Diagnosis
If your dog or cat is experiencing a gradual loss of vision, chances are she is compensating and adapting quite well, which can make it difficult for you to detect vision problems. On the other hand a sudden, complete loss of vision is very obvious.
Some of the signs your pet may be losing her eyesight more slowly include:
- Misjudging heights (for example, your cat tries to jump as she normally would from one object to another, but lately she doesn't always make it)
- Bumping into things (for some pets with gradual loss of vision, even the transition from carpet to tile can throw them)
- Showing confusion in new or changed surroundings (this can include furniture rearrangement, or moving the food or water bowl to a different location)
- General clumsiness and disorientation; being easily startled
- Eye rubbing; squinting; cloudy, discolored or inflamed-appearing eyes; excessive tearing; abnormally large pupils
Diagnosis of a partial or complete loss of vision can be made with a thorough eye examination performed by a veterinary ophthalmologist.
Congenital blindness isn't something you can prevent in your pet, but many causes of acquired blindness are entirely within your control.
- Examine your pet's eyes regularly, and make an appointment with your veterinarian if his eyes change or look different, or if you notice personality or behavioral changes.
- Keep your pet at a healthy weight and feed a low carbohydrate, species-appropriate diet. This will dramatically reduce the likelihood of diabetes, which can lead to blindness.
- Allow your dog to maintain his sex hormones as he's maturing, as this may reduce the incidence of adrenal disease, which has been linked to SARDS.
- Feed a fresh food diet that is high in antioxidants, including lutein, lycopene, vitamins C and E, beta-carotene, and astaxanthin. This will help nourish and support your pet's eye health throughout his life.
Caring for a Pet with Vision Loss
There are many things you can do as the guardian of a partially or completely blind pet to help your companion feel secure and comfortable at home. For example:
- Avoid moving furniture around; don't leave objects in hallways
- Also avoid moving food and water bowls, bedding, and litter boxes – consistency and routine are even more important to pets with poor or no vision
- Make sure your pet has a safe spot she can access easily
- Cover sharp corners or objects with something soft to prevent injuries and unnecessary trauma
- Place barriers at the top and bottom of staircases, around the pool if you have one, and any area where your pet might fall; if necessary, carry your pet up and down stairs and wherever else she might stumble or take a tumble
- Always supervise your visually impaired pet when she's outside
- When you enter a room where your pet is, avoid making loud sounds or startling her; speak softly to her before touching or petting her
Rosco, my now-departed Boston Terrier sweetheart, lost about 80 percent of his vision and went completely deaf in the last few years of his life. When he was sleeping and I needed to move him, there was no point in speaking softly to him because he couldn't hear. If I touched him, he awoke startled, so I would gently blow on him, which helped him wake up in a calmer state. It also kept his cortisol levels low so he felt comfortable in his environment even though he couldn't see well or hear.
One exceptional resource I recommend to all my clients with blind pets or pets with vision loss is Caroline Levin's book Living with Blind Dogs: A Resource Book and Training Guide for the Owners of Blind and Low-Vision Dogs. If you have a pet who is blind or is losing his vision, I highly recommend this book.
Recently I also ran across a potentially helpful device developed by the loving owner of a toy Poodle who is going blind. It's called Muffin's Halo Guide for Blind Dogs. You can read the backstory here.