Trichiasis refers to an acquired condition in which eyelashes emerging from their normal anterior origin are curved inward toward the cornea. Most cases are probably the result of subtle cicatricial entropion of the eyelid margin. Trichiasis can be idiopathic or secondary to chronic inflammatory conditions.
Distichiasis is a congenital (often autosomal dominant) or acquired condition in which an extra row of eyelashes emerges from the ducts of meibomian glands. These eyelashes can be fine and well tolerated or coarser and a threat to corneal integrity.
Aberrant eyelashes emerge from the tarsus as a result of chronic inflammatory conditions of the eyelids and conjunctiva such as trachoma, ocular cicatricial pemphigoid, Stevens-Johnson syndrome, chronic blepharitis, or chemical burns.
Aberrant eyelashes and poor eyelid position and movement should be corrected. Aberrant eyelashes may be removed by epilation, electrolysis, or cryotherapy. Mechanical epilation is temporary because the eyelashes will normally grow back within 2–3 weeks. Electrolysis works well only for removing a few eyelashes, although it may be preferable in younger patients for cosmetic reasons. Cryotherapy is still a common treatment for aberrant eyelashes, but freezing can result in eyelid margin thinning, loss of adjacent normal eyelashes, and persistent lanugo hairs that may continue to abrade the cornea. Treatment at –20°C should be limited to less than 30 seconds to minimize complications. The preferred surgical technique for aberrant eyelashes is a tarsotomy with eyelid margin rotation. For further discussion, see BCSC Section 7, Orbit, Eyelids, and Lacrimal System.