distichiasis

Distichiasis is a condition in which an abnormal second row of eyelashes emerges from the openings of the Meibomian glands along the eyelid margin. These lashes typically arise at the posterior edge of the lid and can rub against the cornea or conjunctiva, leading to irritation, tearing, and potential corneal damage. Distichiasis can be congenital or acquired.

In humans, congenital distichiasis often occurs as part of lymphedema-distichiasis syndrome, caused by mutations in the FOXC2 gene and inherited in an autosomal dominant pattern with variable expressivity. Acquired cases may follow scarring, inflammation, or previous ocular surgery.

Clinical features include chronic eye irritation, tearing, conjunctival redness, and, with ongoing contact with the cornea, keratitis or corneal ulcers. Distinguish it from trichiasis, where misdirected lashes arise from any part of the lid margin, and from epiblepharon, where skin folds push lashes against the eye.

Diagnosis is typically made by slit-lamp examination with eyelid eversion to identify posteriorly arising lashes, along with evaluation for corneal or conjunctival damage. Additional imaging is rarely required.

Treatment depends on severity and symptoms. Some individuals require no treatment. Symptomatic cases may be managed with temporary hair removal (epilation). Definitive therapies include cryotherapy, argon laser or CO2 laser ablation, electroepilation, or surgical destruction of lash follicles. Similar approaches are used in animals, particularly dogs with breed predispositions, sometimes with recurrence requiring repeat procedures. Prognosis varies with severity and recurrence, and management of any associated conditions is important in congenital syndromes.