Entropion and Ectropion
Entropion is a condition in which the eyelid is turned in against the eyeball. Ectropion is a condition in which the eyelid is turned outward and does not come in contact with the eyeball.
Normally, the upper and lower eyelids close tightly, protecting the eye from damage and preventing tear evaporation. If the edge of one eyelid turns in (entropion), the eyelashes rub against the eye, which can lead to ulcer formation and scarring of the cornea. If the edge of one eyelid turns outward (ectropion), the two eyelids cannot meet properly, and tears are not spread over the eyeball. These conditions are more common in older people (generally the result of tissue relaxation with aging) and in those who have had an eyelid injury that caused scar formation.
 See the figure Using Eye Drops and Eye Ointments.
Both entropion and ectropion can irritate the eyes, causing watering and redness. Eye drops and ointments can be used to keep the eye moist and soothe the irritation. Occasionally, entropion can lead to corneal ulcer (see Section 20, Chapter 230). Entropion and ectropion can be treated by surgery--for instance, to preserve sight if damage to the eyes (such as corneal ulcer with entropion) is likely or has occurred, for comfort, or for cosmetic reasons.
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