Normally the conjunctiva does not cover the surface of the cornea, which is a translucent mucous membrane covering the surface of the sclera and the inner surface of the eyelid. The conjunctiva is not part of the wall of the eye, whereas the cornea is part of the outermost layer of the wall of the eye and is located directly in front of the eye. The cornea is transparent, and the cornea and conjunctiva are two different tissues that are not identical in structure and do not have the same function. However, the conjunctiva and cornea are adjacent to each other, and inflammation of each other can spread to each other. For example, in conjunctivitis, the cornea may be involved causing symptoms of keratitis, inflammation of the cornea can cause conjunctival congestion, and when the stem cells of the corneal limbus are dysfunctional, conjunctivalization of the corneal epithelium can occur. In addition, in the case of pterygium, the degenerated conjunctival tissue grows into the cornea and covers the cornea.