Diagnosing conjunctivitis is based on the physical exam finding of a red, inflamed conjunctiva, usually with associated tearing or other eye discharge. Diagnosing the underlying cause in order to provide precise treatment is difficult. Your veterinarian will probably perform the following tests: A thorough eye exam to detect any foreign material such as sand, plastic or grass. It can also detect any abnormal eyelid conformation or inflammation of the eyelids, cornea, or within the eye.
An eye pressure test to detect glaucoma. This eye disease produces enlargement of the blood vessels under the conjunctiva and can easily be mistaken for conjunctivitis.
Schirmer tear test to determine if your cat's eyes produce an adequate amount of tears. Inadequate tear production results in keratoconjunctivitis sicca (dry eye), which causes conjunctivitis.
Fluorescein staining to reveal corneal lesions. The test is done by placing a drop of dye on the surface of the eye, then flushing so the eye can be examined. If stain is present on the surface of the eye, there has been disruption of the surface of the cornea, such as an abrasion, scratch or ulcer.
In addition to these tests, your veterinarian may recommend additional tests.
Conjunctival scraping and examination of the conjunctival cells to help identify the type of inflammation present and search for viruses
Certain blood tests if the animal is acting ill
Since many cases of conjunctivitis are mild and respond to topical anti-inflammatory medications, your veterinarian may chose to prescribe such a drug before proceeding with additional diagnostics. If the conjunctivitis does not resolve in five to seven days, or if it recurs immediately after the medication is stopped, further tests may be needed. For cats with conjunctivitis associated with upper respiratory infection, supportive care is usually administered until the cat starts to recover. The eye is frequently treated with terramycin ointment or some other antibiotic to treat any chlamydial and bacterial agents involved.
If an exact cause can be determined, the specific treatment is instituted for that cause.
For cats with chronic, recurrent conjunctivitis associated with feline herpesvirus, topical anti-viral medications may be instituted, although they are expensive. In addition, some of these cats respond to oral lysine given for long period of time.
Eye irritants such as pieces of sand, plastic, or grass can be flushed out of the eye using copious amount of sterile eye irrigation fluid. After removal of the offending foreign matter, a brief course of antibiotics or antibiotic steroids usually resolves the conjunctivitis.
Conjunctivitis due to environmental irritants can be difficult to treat unless the irritant can be removed. Owner's should avoid smoking around the cat, should avoid the use of spray carpet cleaners and other agents that might linger in the environment. Furnace and air-conditioning filters should be changed regularly, and air filter or humidifiers may be helpful in some cases.
Corneal ulcers are generally treated with topical antibiotics and sometimes with pupil dilators. Many corneal ulcers heal within three to five days.
If dry eye is diagnosed, topical artificial tears and lubricants may relieve the conjunctivitis. Other potential medications include a trial of topical cyclosporine, which may increase tear production, anti-viral drugs for associated herpesvirus, topical antibiotics and anti-inflammatory drugs.
Allergic conjunctivitis is treated with topical steroids. This can alleviate some of the redness and inflammation. Removal of the item your cat is allergic to can also help eliminate the disease, but frequently this is not possible.
Inflammation of the eyelids and cornea must also be addressed.