In the photo above, Bubba was relaxed, but anticipating a leap to the shoulder of the photographer. His eyes were wide open, clear, and alert, although his narrowed pupils reflected the shaft of sunlight shining off his left eye. As in humans, a cat's pupils should normally be of the same size. A change in the size of the pupil in one eye can indicate a number of conditions, ranging from mild to serious. They include:
- Inflammation of the eye
- Horner's syndrome (a neurological disorder)
- FeLV (may cause pupillary spasms)
- Central nervous system injury
The "Third Eyelid"
Cats have an inner, third eyelid, called a nictating membrane (also spelled "nictitating"), which serves to protect the eye from dryness and/or damage. When a cat is sick, the third eyelid will partially close, which is a signal to get him to the vet immediately if other symptoms present. Curiously enough, a very happy cat will also show that nictating membrane.
- Moody Eyes
Like many other physical characteristics of the cat, his moods are reflected by his eyes. Pupil size changes are the clue: an angry cat will have narrowed pupils, while an excited or frightened cat will have eyes wide open, with large pupils. A mellow, happy cat's eyes will sometimes appear a shade darker than normal. I can't explain this one; it's just an observation.
From "What Makes Cats Work"
Because cats' eyes are so important to their general welfare, it is crucial that you take your cat to a veterinarian at the first sign of trouble. Many conditions can be treated easily if caught in time, but can lead to months of veterinary expense and possibly even blindness, if ignored.
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