Entropion is a condition in which the eyelid margin turns in against the eyeball, or inverts. This inversion causes the eyelashes to rub against the surface of the eye.
Entropion usually occurs when the upper or lower eyelid loses elasticity as a person ages. The eyelid margin tends to fold inward toward the eyeball.
Entropion usually involves the lower lid, and can be caused by:
When there is involvement of the upper lid, it is usually related to long-standing inflammation. A common cause is trachoma, an eye infection that is present in many Third World nations and related to eyelid hygiene.