There are four types of cataracts in pets.

  1. Inherited, or genetic. This tends to occur in younger animals (younger than 8 years old) of certain breeds.
  2. After an injury. Some eye injuries can cause cataracts as the eye heals.
  3. Associated with disease. Some diseases, like diabetes, can cause cataracts as a side-effect of the disease.
  4. Related to age. As animals (and people) get older, the lens inside the eye ages, too. As the lens gets older it can develop a cataract.

In a normal eye, the lens is clear and lets light through all the way to the back of the eye. This is how we see – by light getting to the retina on the back of the eye. As animals (and their eyes) age, the lens can get cloudy. When the lens gets cloudy, the light can no longer reach the back of the eye. This can make it difficult for your older pets to see.

The diagram below shows a normal eye, with light passing all the way through the lens. The inset shows a lens with a cataract – the light can not get through the lens to the back of the eye.

eye diagram-cataract

Image from ePetHealth.

Below is a photograph of a dog with a normal eye. This is probably what your dog’s or cat’s eye looks like. The brown part of the eye is the iris, and the black part in the middle is the pupil. The lens is behind the pupil, but it is clear so you can not see it.

normal eye

Image from Diagnostic Imaging Atlas.

This is a photographs of a dog with a cataract. The iris looks the same, the circle of brown around the edge of the eye. But instead of a black pupil and a clear lens, you can see the cloudy lens through the pupil. This is a severe cataract, and this dog most likely cannot see out of this eye.

cataract eye

Image from Diagnostic Imaging Atlas.

Cataracts can affect an animal’s vision. If the cataract takes up less than 30% of the lens, or if only one eye is affected, your pet will not have much trouble seeing. But as the cataracts get bigger (taking up 60% of the lens or affecting both eyes) you may notice signs that your pet can’t see as well as before. If cataracts affect the entire lens, your pet will not be able to see out of that eye.

Some things you may notice with vision impairment are:  walking into things, tripping over things left on the floor, or moving more slowly, especially in low light. Many pets can compensate very well with reduced or no vision. Some things you can do to help are not moving furniture, food bowls, or litter boxes; going slow on walks; letting friends and family know that your pet has trouble seeing and they should be careful when handling them.

Unfortunately, there is no prevention for cataracts. A veterinary ophthalmologist can perform surgery to remove the cataract. Although we do not perform this surgery at the Princeton Veterinary Hospital, we can refer your pet to a veterinary ophthalmologist for a consultation to see if surgery would be a good option.


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