External eye diseases.

Diseases of the external eye can have several causes and many have similar symptoms, but a precise diagnosis of the specific disorder is crucial for proper treatment. Evaluation should begin with a complete medical history to ascertain any systemic disease that may affect the eyes. Physical examination should include determination of visual acuity, inspection of the tarsal and bulbar conjunctiva, and microscopic evaluation of the cornea. When external inflammatory disease is present, laboratory testing is required. Smears and cultures are the only reliable methods to determine the specific organism causing the infection. Treatment is then aimed at eradicating the underlying microbes.