Ocular choristomas.

Choristomas are congenital lesions representing normal tissue(s) in an abnormal location. They are the most common epibulbar and orbital tumors in children. Epibulbar choristomas affect the cornea, limbus or subconjunctival space, and range in appearance from a small, flat lesion to a large mass filling most of the epibulbar region. Astigmatism is often present. Choristomas may be associated with coloboma, Goldenhar syndrome or epidermal nevus syndromes; those associated with the latter are often bilateral and extensive. Choristomas are occasionally familial. Surgery may be indicated to improve vision or cosmesis, or to impede growth. Although choristomas most commonly involve the epibulbar area, they can affect many areas of the eye and orbit, and often affect more than one area.