Conjunctivitis is a common diagnosis in patients who complain of a red eye. It is usually a benign or self-limited condition, or one that is easily treated. Other causes of red eye are discussed elsewhere.
This topic will review the clinical manifestations, diagnosis, and treatment of conjunctivitis. Other conditions which may be confused with conjunctivitis include acute angle-closure glaucoma, iritis, uveitis, and infectious keratitis. In contrast to acute conjunctivitis, these conditions are sight-threatening and must be managed by an ophthalmologist.
DEFINITIONS AND ANATOMY
Conjunctivitis literally means “inflammation of the conjunctiva.” The conjunctiva is the mucous membrane that lines the inside surface of the lids and covers the surface of the globe up to the limbus (the junction of the sclera and the cornea). The portion covering the globe is the “bulbar conjunctiva,” and the portion lining the lids is the “tarsal conjunctiva”.
The conjunctiva is comprised of an epithelium and a substantia propria. The epithelium is a non-keratinized squamous epithelium that also contains goblet cells. The substantia propria is highly vascularized and is the site of considerable immunologic activity.
The conjunctiva is generally transparent. When it is inflamed, as in conjunctivitis, it appears pink or red on general inspection. Up close, the examiner can discern fine blood vessels, termed “injection,” in contrast to extravasated blood, which is seen in subconjunctival hemorrhage. All conjunctivitis is characterized by a red eye, but not all red eyes are conjunctivitis.
