Because the outside of the eye is in direct contact with the environment, it is susceptible to infections and injuries. There are also a number of hereditary diseases that can impact the outer eye. The major signs of external eye disease are redness that does not improve with treatment and poor vision not explained by retina problems.
One common external eye condition is conjunctivitis (usually called "pink eye"), an infection marked by red, itchy eyes and tearing. Pink eye can be caused by cold viruses, allergic reactions or bacteria. Other common conditions include inflammation of the sclera (the tough outer layer of the eye) and inflammation of the cornea caused by a skin disease known as rosacea.
A common eye injury is corneal abrasion, or damage to the thin outer layer of the cornea often caused by scratches from twigs, fingernails or contact lenses. Symptoms include a burning sensation and the feeling of having “something in your eye." Corneal abrasion can also cause blurred vision. Treatments include ointments, drops and patching, and most abrasions heal within a day or two.
Cornea abnormalities include keratoconus, which literally means “cone-shaped cornea." This protruding of the cornea causes distorted vision. It usually appears in the late teens or early 20s, progresses slowly and then stops after a decade or two. For some patients, vision can be improved with corrective glasses or rigid contact lenses. About one-fifth of all patients with keratoconus will require a corneal transplant-for information, read about the Eye Institute’s Cornea/External Eye Disease Service.