The main observable symptom of cataracts in cats is an icy blue or whitish spot that develops on the pupil of the eye. The spot may appear small and increase slowly over time or the spot may quickly spread over the pupil. A cataract is described as a cloudiness in the normally clear lens of the eye. When the lens becomes cloudy, light is blocked from passing to the retina in the back of they eye. The density of the cloudiness determines the loss of vision.
Cats are known to cover symptoms of illness. A visually impaired cat may become less agile, will be more reluctant to move about in unfamiliar places and will be more cautious about going up and down stairs. As noted, the behavioral signs might be too subtle to notice. Dr. Thomas Kern, DVM, associate professor of ophthalmology at Cornell University’s College of Veterinary Medicine: “The owner should routinely check the cat’s eyes. Look for changes in the color of the iris, for example, or see if the eye seems to be cloudy. If you see anything unusual, have the animal examined by a veterinarian.” Depending on what caused the cataract, early treatment with a variety of medications (antibiotics, anti-inflammatory drugs) may prevent or delay the onset of cataract-related blindness. In some cases, treatment for high blood pressure or diabetes will be effective in slowing the rate at which a cataract progresses.
Therefore, if you see cloudiness in one or both of your cat’s eyes, see a veterinarian immediately. The vet will take a thorough history, perform a complete physical (especially of the eyes), and may order a variety of tests (including blood, urine and more sophisticated tests) to determine the possible cause and severity of the problem. Some of the causes are listed below:
- Diabetes mellitus
- Old age, retinal disease
- Inflammation of the eye’s uvea
- Abnormally low levels of calcium in blood
- Exposure to radiation, toxic substances or drugs
- Injury or trauma -- electrocution, displacement of the lens
In some cases, surgery by a veterinary ophthalmologist may be necessary. In such a procedure, the surgeon will make small incisions first in the cornea and then in the lens capsule before inserting an instrument that uses high-frequency sound to disintegrate and remove the affected lens. Following this procedure, an artificial lens is inserted and the incision is sutured shut. The surgery, according to Dr. Kern, is successful in most cats that have qualified as good candidates for lens implantation.
Dr. Jennifer Weiser provided the best description of a cataract: "A cataract is like a physical barrier to light, similar to a cover over the lens of a camera. This barrier can be physically removed by surgery. In contrast, the retina is like the film in the camera and the rest of the eye is the camera itself. If the camera or the retina is not working properly, then removing the lens cover (cataract) will not improve the animal's vision. The rest of the camera (eye) must be working well, and the film (retina) must be good before removing the barrier over the lens will be worthwhile."
Information for this article was summarized from the following websites: Cornell Feline Health Center, Pet MD, Pet Place (specifically the article "Cataracts in Cats" by Dr. Jennifer Weiser) and Petwave. It should be noted that many of the disease processes, symptoms and treatments are similar for humans. In fact, the Cat Authors' Meowmuh had one cataract removed last month and will have the second removed next month. It takes time for the eyes to heal as well as for the eyes and the brain to learn to work together again. Although there are no guarantees, vision should be improved.