As one ages, the eyelids can droop. When the upper lid becomes droopy, it is called a ptosis. When the lower lid droops this is called an ectropion. When the lower lid turns in, the eyelashes can rub against the eyes and this is called an entropion.
Ptosis is a drooping or falling of the upper or lower eyelid. The drooping may be worse after being awake longer,
when the individual's muscles are tired. This condition is sometimes called "lazy eye", but that term normally refers
to amblyopia. If severe enough and left untreated, the drooping eyelid can cause other conditions, such as amblyopia or astigmatism. This is why it is especially important for this disorder to be treated in children at a young age,
before it can interfere with vision development.
Ectropion is a medical condition in which the lower eyelid turns outwards. It is one of the notable aspects of newborns exhibiting congenital Harlequin-type ichthyosis, but ectropion can occur due to any weakening of tissue of the lower eyelid. The condition can be repaired surgically.
Entropion is usually 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." Repeated cases of 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.