Diagnosing conjunctivitis is based on the physical exam finding of a red, inflamed conjunctiva with associated tearing or other eye discharge. Diagnosing the underlying cause in order to provide correct treatment is sometimes difficult. Your veterinarian will probably perform the following: A thorough eye exam to detect any foreign material such as sand, plastic or grass. It can also detect any abnormal eyelid conformation, abnormal eyelashes, eyelid inflammation and disorders of the cornea.
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 dog'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 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
Certain blood tests if the animal is acting ill