The conjunctiva is divided into two main sections: the palpebral, lining the undersurface of the lids, and the bulbar covering the sclera. It is a translucent mucous membrane that is not easily observable unless irritation of the eye is present. The conjunctiva provides a smooth interface between the lid and eye during blinking. It has two layers: an epithelial and stromal layer. The epithelium crosses at the limbus and is continuous with the corneal epithelium. Goblet cells, which produce the mucoid bottom layer of the tear film, are also located in this layer of the conjunctiva.

Contact lens wearers may experience conjunctival injection if a lens does not fit properly. Excessive mechanical irritation can cause the loosely attached tissue to become edemic and inflamed. The conjunctiva is also susceptible to inflammation of a viral, bacterial or allergic nature. These conditions always contraindicate contact lens wear and must be carefully screened for at every visit.

Noncompliance with this rule would slow down the healing process due to the limited oxygen supply reaching the eye. Furthermore, soft lenses would need to be disposed of in cases of viral or bacterial insult. Reusing the lens would risk re-infection of the eye.