Conjunctivitis

INTRODUCTION

Conjunctivitis is a common patient complaint. It is the most likely diagnosis in a patient with a red eye and discharge. (See "Evaluation of the red eye".)

Acute conjunctivitis is usually a benign, self-limited condition or one that is easily treated. When making a diagnosis of acute conjunctivitis, one needs to make certain that sight-threatening and pathologic processes have been ruled out. In contrast to acute conjunctivitis, these entities, such as acute angle closure glaucoma, iritis, and infectious keratitis, must be managed by ophthalmologists, and will not be discussed here.

DEFINITIONS

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 looks pink or red at a distance. Up close the examiner can discern fine blood vessels, termed "injection," in contrast to extravasated blood, which is seen in subconjunctival hemorrhage. Degenerative, inflammatory, and infiltrative processes can cause the conjunctiva to become opacified, taking on a white, yellow, or fleshy appearance. All conjunctivitis is characterized by a red eye, but not all red eyes are conjunctivitis. (See "Evaluation of the red eye".)