Congenital Eyelid Coloboma

Eyelid colobomas are rare, congenital, full-thickness defects of the eyelid. They may be unilateral or bilateral, affect one or both of the upper or lower lids, and vary in extent from a small notch to an absence of the entire lid. About a third are an isolated finding, with the remainder associated with other ocular and craniofacial abnormalities. Isolated colobomas are typically smaller and involve only the upper lids. These are thought to arise late in embryogenesis due to abnormal eyelid separation. Larger colobomas, and those affecting the lower lids, are more often associated with other ocular and craniofacial abnormalities. These probably arise earlier in embryogenesis with improper fusion of the eyelid folds leading to microphthalmia, conjunctival traction bands, and facial clefts, or with abnormal migration of neural crest cells causing dermoids and ‘1st arch syndromes’. Eyelid colobomas typically present in two clinical situations; either as relative emergencies in neonates due to corneal exposure, or later due to amblyogenic or cosmetic concerns. Amblyopia is present in 60% of coloboma cases. It can arise from high refractive errors and/or astigmatism (often associated with limbal dermoids), from opacities of the ocular media, or from conjunctival traction bands. Refraction and forced duction testing should be considered essential in the assessment of a child with coloboma. Half of children require surgery before the age of one in order to protect the cornea, and/or to release conjunctival bands. ‘Lid-sharing’ flaps such as the Mustarde lid switch flap are the technique of choice for large upper lid colobomas.