Blindness In Dogs And Cats
Do you think your dog isn’t seeing so well? Have you noticed your dog bumping into things at night? Did you know that dogs and cats can lose their vision? There are numerous diseases and conditions that can lead to reduced vision and blindness in dogs and cats. In the following article, I will discuss some of those causes as well as some of the testing and treatment options available.
Dogs and cats see things a little differently than we do as humans. There are perception differences, color differences, and perspective differences. For example, ever stop and picture the world as a dog or cat sees things? What would you do to get this picture, I bet you would bend down to the level of a dog and cat! Dogs and cats see the world from only a few feet off the ground. Tall grass, bushes, and benches all can obstruct a dog’s view from this point of view. Dogs and cats also hunted and foraged in the wild for food in the day and at night. For these reasons, they have adopted different mechanisms that enable them to see the world a little differently than you and I.
Despite the old myth, dogs and cats do see color, although perhaps a little differently than we do. Dog’s color palette tends to focus more on yellow and purple/blue with a little less ability to see red. In addition, dogs and cats tend to have a wider visual range than we do but with more focus/clarity off-center than directly in the middle. Cats and dogs also have better night vision than we do owe to the fact that the back of their eyes has a hyper-reflective area called the fundus.
Although these adaptations allow certain improvements or differences from humans, they are still susceptible to ocular disease. While there are too many ocular diseases to discuss all of them in this article, it may be helpful to break them down into 3 distinct categories: The inability for sufficient light to reach the back of the eye, the inability for the retina to process these images, or an inability of the brain to decipher the signals sent in order to generate an image in the brain.
Cataracts are one diagnosis which may interfere with light transmission to the eye. Cataracts are a hardening of the lens capsule which the light passes through on its way to the back of the eye. An example of retinal disease is retinal detachment which can be seen most commonly in cats with high blood pressure. Finally, central brain disease may interfere with the ability to translate signals into images and while the eyes may be functioning quite well, the brain is unable to process the images sent. Other ocular diseases include diseases of the cornea or external structures like the conjunctiva or sclera or the eyelids. These disorders include corneal ulcers, entropion, dry eye, cherry eye, and many others.
Regardless of the cause, if you suspect your pet is losing their vision, they should be evaluated by a Veterinarian immediately. Some ocular disease can progress rapidly leading to vision loss or even loss of your pets eye! When you visit your veterinarian, they take a complete history to determine when you noticed a problem, what you are observing if changes are noted between day and night, and if any other diseases or conditions have been diagnosed which may be contributing to ocular dysfunction. After a thorough history, appropriate tests will be recommended to help determine where and why you are noticing a problem. For external problems involving the cornea, your veterinarian may place a special stain on the eye to help identify ulcers which are scratches on the surface of the cornea. For intra-ocular disease, an ophthalmoscope, special lenses, and lights may be used to help look into your pet’s eyes past the exterior structures. Fortunately, all of these are readily available at most veterinary hospitals and are inexpensive tests to perform.
Many ocular diseases are treatable especially if caught early. If you suspect your dog or cat has poor vision, please call one of our Veterinary Offices to schedule an appointment with a member of our veterinary team.
Jeffrey Stupine VMD
World of Animals Veterinary Hospitals