Also known as "pink eye," conjunctivitis occurs when the mucous membrane that lines both the outside of the eyeball and the inside of the eyelid becomes inflamed. As with pink eye in humans, this condition is highly contagious, although the feline version can only be passed between cats.

• Causes: Conjunctivitis typically results from an upper respiratory illness caused by either a virus or a bacterial infection, says Cornell University College of Veterinary Medicine.
• Signs and symptoms: The most telling symptom is runny eyes. Eye discharge might be clear or be gray, yellow, green or even a dark, rusty red color. The inside of the eye may appear swollen and/or reddened, and either one or both eyes may be affected. Other signs of upper respiratory illness, such as sneezing or nasal discharge, might also be present.
• Treatment: Typically, conjunctivitis is treated with topical antibiotics in the form of drops or ointment. If an upper respiratory illness is present, your vet may treat that as well. One type of infection that often results in this eye disorder is FHV-1, or Feline Herpes Virus. If this is determined to be the cause, your veterinarian may prescribe further treatments to control this virus and prevent further flare-ups.

While cats don't generally suffer from the type of allergies that result in itchy, watery eyes, irritants in their environment can produce a similar effect.

• Causes: For cats, eye irritants can include strong fragrances, such as perfume, cleaning chemicals, tobacco smoke and dust. Just about anything that gets in your cat's eye can cause an irritated reaction.
• Signs and symptoms: Watch for signs of discomfort such as squinting or rubbing, as well as redness and discharge. If it's clear that irritation is causing your cat's symptoms and they're willing to allow it, try rinsing out their eyes with an eye-wash solution. However, because symptoms of irritation are nearly identical to those of more serious conditions, it's best to consult your vet if you notice any signs of eye discomfort. It's also a good idea to remove the irritant from the home if you are aware of what is causing their discomfort.

This condition results from pressure in the eye caused by a buildup of excess fluid. Glaucoma is a serious condition that should be treated as quickly as possible in order to prevent permanent blindness or disfigurement.

• Causes: A number of things can prevent eye fluid from draining, leading to the buildup that causes glaucoma. These include anatomical abnormalities, eye infections, inflammation, eye trauma and tumors. Some cats have a genetic predisposition toward this disorder, in which case it's not uncommon for both eyes to be affected.
• Signs and symptoms: Cats experiencing glaucoma will generally show signs of significant pain, which may include eye rubbing and squinting, withdrawing from people and yowling or crying. Eyes may appear cloudy, runny or reddened. In severe cases the eyeball itself may appear swollen.
• Treatment: If you suspect your cat might be suffering from glaucoma, get them to a vet immediately. The sooner the increased pressure within the eye can be reduced, the better the chance of saving the eye. In mild cases, glaucoma resolves itself once the underlying cause is dealt with, but more severe cases may require ongoing management to prevent excessive fluid buildup. In the worst cases, it may be necessary to remove the eye.

If your cat is showing any signs of eye problems, it's important that you take them to a vet right away. Because various conditions share so many symptoms, it's impossible to diagnose eye problems correctly without an examination. Trying to guess what the problem is or waiting to see if it will clear up on its own wastes time that could be crucial to saving your cat's eye if the condition turns out to be serious.

Regardless of whether your cat shows any signs of eye problems, good cat eye care can help prevent such problems from developing in the first place. Feeding your cat a high quality meat-based cat food, staying up-to-date on vaccinations, keeping them indoors and limiting their exposure to strange cats who might be contagious can all go a long way toward protecting your cat's eyes—not to mention their overall health and quality of life.