Conjunctivitis is an inflammation of the tissue that lines the inside of the eyelid and covers the surface of the eye. It is a very common eye problem in cats and can be caused by allergies, bacteria, viruses, or foreign bodies such as dirt or sand. Conjunctivitis can cause the eye to appear red and inflamed, and your cat may also have discharge from the eye. A more robust list of symptoms of conjunctivitis includes redness, swelling, discharge, and squinting. Conjunctivitis is usually treated with eye drops or ointment. Ultimately, though, it's best to consult with a veterinary ophthalmologist to get a proper diagnosis and ensure that your cat receives the right treatment.