by Barry B. Burtis D.V.M.
Blindness in Cats
Cats are well known for their good eyesight. The old wife's (or husband's) tale says that they can see in the dark. However, just like other animals there are a number of causes of blindness than can affect them.
It can sometimes be very difficult to accurately assess a cat's vision. Vision can be assessed in dogs using an obstacle course. This is often difficult with cats. Some cats with normal vision may freeze when placed in a room or may move around very slowly and with caution. On the other hand, cats that have been blind for a while may start moving around and exploring the room. Cats can adapt very well to a gradual loss of vision. If they are living in familiar surroundings blindness may go undetected even by observant owners. A thorough physical examination by a veterinarian and perhaps even a visit to a veterinary eye specialist will be required to diagnose some kinds of blindness in cats.
Diseases of the cornea, the front, clear, glassy part of the eye can be a cause of loss of sight. Feline Herpes virus infections are one of these diseases that can affect cats. These viruses can be spread from cat to cat. This infection may cause the normal transparent cornea to be replaced by thick, red, tissue. This will impair vision but usually not cause total blindness. However, if bacterial infections complicate this stage of the problem the lesion may progress to cause blindness. Eye injuries that result from trauma - fights with other cats - or other perforating eye damage can lead to severe scarring of the cornea that will affect the eyesight.
Cataracts affect the lens of the eye and can cause blindness in dogs and cats. In dogs cataracts are a common genetic or inherited disorder. Inherited predisposition to cataracts in cats is rare. Diabetes commonly causes cataracts in dogs but not in cats. In cats cataracts are most commonly caused by a chronic infection or inflammation in the fluid in the front part of the eye - called an anterior uveitis.
Glaucoma is a blinding disease in both dogs and cats. Clinical signs of glaucoma in cats often develop much more slowly and may be more difficult to recognize than in dogs. Most commonly owners notice an increase in the size of the eye, a cloudy appearance of the eye and an increase in the size of the pupil in the eye. These changes are often reported to have gradually developed over several months. Once diagnosed, prompt medical or surgical treatments will be needed for glaucoma.
Older Siamese cats appear to be the breed most predisposed to retinal degeneration, another cause of blindness in cats. Nutritional deficiencies, inflammatory diseases, genetic abnormalities as well as certain toxic materials can all lead to retinal disease.
High blood pressure is commonly a cause of a number of retinal diseases in cats that may cause blindness. Retinal hemorrhages, retinal edema or retinal detachment are examples. Hypertension or high blood pressure is frequently associated with chronic renal failure or hyperthyroidism in cats. Both these diseases are being recognized more often these days likely as a result of cats living longer. Primary hypertension appears to be uncommon in cats but can occur. There are drugs that usually work very effectively at controlling hypertension in cats. With control, the resolution of retinal problems, including the re-attachment of a detached retina becomes a possibility.
There are also tumours that can cause blindness in cats. The most common cancers that can affect inside parts of the eye are iris melanomas and lymphosarcomas. Finally, there a group of neurologic diseases that cause loss of sight in cats. With this group of diseases a blind cat will have normal appearing eyes on eye examination.
Making sure your cat has healthy eyes and good vision is another responsibility of being a good cat owner. Be aware for any signs that might indicate a loss of vision in your pet. Take precautions to try and ensure your cat does not sustain any injuries to their eyes. Maintain your cat's good general health to reduce the risk of diseases that can result in eye problems. Seek veterinary care promptly if you notice any change in the appearance of the eyes or the ability of your cat to see well.