The lower eyelid is held in position by a strong tissue called the canthal tendon. This structure can weaken with age, causing the eyelid to turn either inwards or outwards.
When the eyelid turns outwards, it is called ectropion. Patients with this condition frequently experience redness, irritation, and watering/tearing. When the eyelid turns inwards, it is called entropion. This inward rotation of the eyelid often causes the eyelashes to rub against the cornea, causing a significant amount of discomfort and mucusy discharge with tearing. It can even lead to corneal abrasion and/or infection (corneal ulcer). Patients with entropion are typically much more uncomfortable than those with ectropion and have their condition repaired at an earlier stage.
In both of these conditions, the root cause of the problem is a laxity or weakness of the suspensory canthal tendon. Correcting these conditions is often the same procedure, where a portion of the eyelid is removed and the tendon is tightened to restore a more natural anatomy.