Entropion is a condition in which the eyelid (in most cases the lower lid) folds inward. It will cause pain and discomfort, as the eyelashes constantly rub against the cornea and irritate it.
Entropion in most cases it is caused by genetic factors and very rarely it may be congenital when an extra fold of skin grows with the lower eyelid (epiblepharon) Entropion can also create secondary pain of the eye (leading to self trauma, scarring of the eyelid, or nerve damage). The upper or lower eyelid can be involved, and one or both eyes may be affected.
When entropion occurs in both eyes, this is known as “bilateral entropion.” Trachoma infection may cause scarring of the inner eyelid, which may cause entropion. In human cases, this condition is most common to people over 60 years of age.