It is an “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 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.
Conjunctivitis can be classified as infectious or noninfectious and further divided into four main types:
The prevalence of each is different in pediatric and adult populations. Bacterial conjunctivitis is more common in children than in adults. Although published studies suggest that the majority of cases in children are bacterial, the prevalence of bacterial conjunctivitis seen in studies presumably reflects the greater likelihood that patients with copious discharge will present for care. Clinical experience suggests that most infectious conjunctivitis is viral in both adults and children.