It's hard not to be impressed with the beauty of a cat's eyes. From their almond-shaped pupils to the intense iris coloration, they are truly remarkable.
However, just as we say that in humans the eyes are the windows to the soul, in cats they're often a window into their health status. And as any veterinarian will tell you, cats give us very few clues that they're unhealthy, so it's important to pay attention to the subtle changes we observe.
Read on the find out what your cat's eyes could be telling you about his health.
Eye discharge in cats
At PetCoach we get asked about eye discharge in cats very frequently. It's probably the number one eye-related complaint from cat owners. Owners frequently notice excessive tearing from one or both eyes. In general, it's a response to irritation, and can be from a number of causes. Probably the most common cause of excessive tearing, or epiphora, in cats is infection with the herpes virus.
It's estimated that as many as 80% of the house cats in the U.S. are infected with feline herpesvirus; however most of them never show any signs of it. Some of them battle it once in their lives, when they're kittens with immature and/or weakened immune systems, and never deal with it again. Others have intermittent infections their entire lives that show up whenever they are under stress. Sometimes we'll see a little sniffling and sneezing, but by far the most common sign of chronic herpesvirus infection is excessive tearing.
Typically, once the cat's immune system gets things back under control, the infection goes back to its dormant state, and there's no need for medications. The amino acid lysine does seem to help slow viral replication and help the signs resolve faster.
If your cat suffers from the herpesvirus talk to your vet about using lysine. And also be on the lookout for signs that there's a secondary bacterial infection going on as well. If the discharge turns cloudy, especially if it's green or yellow, your cat may need treatment with an antibacterial eye ointment.
Melanoma is a scary form of cancer in humans, and it is in pets as well. A melanoma is a tumor that originates in the cells of the skin that produce the black pigment melanin. While dogs often get these malignancies in the mouth or on the foot, in cats the most common location is in the eye.
Usually owners notice a dark spot on the iris of their cat's eye. The cat typically doesn't show any changes in behavior or activity, and otherwise the eye appears normal. These tumors can also grow in the back of the eye, where they can't be seen without an ophthalmoscope (the tool your vet uses to look into the back of your cat's eye). This is another great reason to make sure that your cat sees your vet for yearly exams, even if he or she appears healthy.
Not all dark spots on the iris are cancerous. Cats can also get iridial cysts, which are benign, but look very similar to iris melanomas. Your vet or a veterinary ophthalmologist can usually tell the difference with a thorough exam of the eye, including measuring eye pressure. Iris melanomas can cause glaucoma and blindness, and they can spread throughout the body if not treated early. This usually means enucleation, or removal of the eye, and if the cancer hasn't spread to the lymph nodes and beyond, the cat is cured.
Age-related iridial atrophy
A common change to the iris of older cats is known as iridial atrophy. The muscle that controls the enlargement and narrowing of the pupil in response to light or other stimuli is called the ciliary body. Just like many other muscles in the body, with age this muscle can become somewhat sluggish. This sometimes manifests itself as one pupil appearing slightly asymmetric when compared to the other.
It's important to note that this is usually a very slight change, and significant differences in pupil size can be the sign of several serious diseases (read on for more on this topic). Any change in pupil appearance should be checked out by your vet.
Often we'll notice that the cat's eye is being held slightly closed, almost like they're constantly winking at us. In most cases this indicates discomfort. It's called blepharospasm, and it means that the muscles controlling the eyelids are spasming in response to pain. This is a very common finding in another type of feline eye problem known as a corneal ulcer.
Corneal ulcers can result from trauma to the eye, such as getting a scratch from a bush outdoors or from another cat's claw in a fight. Cats with chronic herpesvirus infections are also at risk for development of corneal ulcers. Cats with flat faces, like Persians, often have bulging eyes, and this predisposes them to ulceration due to chronic dryness.
Corneal ulcers can be very slow to heal, and they're another one of the reasons why you should get any signs of eye trouble in your cat checked out. Cats with ulcers typically need antibacterial ointments and pain relief, as they can be incredibly painful. E-collars are often used as cats experiencing eye discomfort frequently want to rub their faces on something, such as a piece of furniture, which complicates healing. Occasionally surgery is needed to remove ulcerated tissue and aid growth of healthy corneal cells.
This fancy word means unequal pupil size. As mentioned above, this may be a normal age-related change. However, there are some serious disease processes that can cause one pupil to appear different from the other, and anytime you notice anisocoria you should get it checked out by your vet.
Anisocoria may be a response to a systemic disease that's affecting the entire body but causing changes to the eye. Your vet may recommend blood work to look for some of these diseases, and which ones are most likely depends on where you live and your cat's lifestyle. And since the nerves that control pupil enlargement and constriction originate in the brain, anisocoria may indicate a lesion in the brain that's affecting the performance of this nerve. So a complete neurological evaluation is warranted when anisocoria is noted.