Cataract is a disease of the lens of the eye in which the normally clear lens becomes opaque or white. You may see the whiteness of the eye when you look at your cat. This interferes with vision and can result in blindness. In some cases, if the cataract is causing significant problems, an eye specialist may be able to operate on the eye to remove the cataract.
Light enters through the front of the eye and is focused by the clear lens onto the retina, at the back of the eye. Information from the retina is transmitted to the brain when processing occurs.
For the lens to work correctly it must be perfectly clear. When a cataract develops, the lens becomes opaque (like frosted glass) or even completely white. Light cannot pass through so well and vision is reduced. Severe cataracts cause blindness.
Cataracts most commonly develop in cats after severe inflammation in the eye, or as a result of poisonings or nutritional imbalances. Some cats are born with cataracts or develop them soon after birth and they may develop due to nutritional abnormalities, or trauma. Diabetes mellitus is a common cause of cataract in dogs but it rarely causes cataract in cats. Lens opacification increases with age and almost all older cats will be affected to some degree although this may not affect their lifestyle at all.
Usually owners are alerted to the fact that their pet may have a problem when they notice a whiteness of the eye. If eye disease develops gradually animals are often able to adapt well and use their other senses to help them get around. Cats have very good hearing and a sense of smell and can use these to compensate for poor vision to some extent. In familiar surroundings it may be almost impossible to tell that a pet cannot see. If you are worried about your pet’s vision you can test it yourself using some simple exercises:
- Observe your cat carefully in the home environment and out of doors
Does he appear to be having any visual difficulty?
- Throw light, silent objects (e.g. a ball of cotton wool) in front of your cat’s eyes
Does he see and follow these?
- Construct a small obstacle course in the home, or move furniture around and away from the usual positions
Does he see and avoid these obstacles the first time?
Repeat the above tests in daylight and in subdued lighting.
If you are concerned about the results of the report them to your veterinary surgeon and ask for a check-up for your pet. Diagnosis is usually straightforward, and based upon visual testing and examination of the eye by a vet/ophthalmologist. Additional tests may be required to check for other causes and other eye diseases.
Cataracts are treated by removing the lens from the eye. The lens is surgically removed by a specialist eye surgeon. There are several different techniques but one of the most popular is known as phacoemulsification (the use of ultrasound waves to break up the cataract). Once the lens has been broken up fragments can be removed through a small incision in the eye. Other surgical techniques are also possible and may be indicated in certain cases, eg when lens of the eye has become displaced.
Following surgery the aftercare is very important. Eye drops may be required for several months and must be applied regularly at home. If cataracts are present in both eyes, they may be removed at the same time, thus avoiding the need for further surgery in the future.