The eyelids are an important part of the ocular adnexa. They provide a mechanical barrier against the environment, distribute the tear film, and remove debris from the ocular surface. In the normal eyelid, the margins should be symmetric and parallel to one another. The upper margin should rest 1 to 2 mm below the superior edge of the cornea, and the lower margin should rest at the inferior edge of the cornea. Generally, the lateral canthus is positioned approximately 1 mm higher than the medial canthus, giving a slight upward slant to the palpebral fissure as one moves laterally.
CONGENITAL ANOMALIES OF THE EYELID
Cryptophthalmos, Ablepharon, and Ankyloblepharon
Congenital anomalies of the eyelid are rare and result from improper or absent differentiation during embryogenesis. The most severe congenital eyelid anomaly is cryptophthalmos, the partial or complete absence of ocular adnexal structures including the eyebrow, palpebral fissure, and conjunctiva. In this condition, skin is continuous over the globe and passes from forehead to cheek without interruption. Visual prognosis is poor as the underlying cornea is often malformed and fused with the overlying skin. In contrast, ablepharon is the absence or severe hypoplasia of the eyelids. Affected individuals require surgical intervention in order to protect and cover the ocular surface. Ankyloblepharon is the fusion of part, or all, of the upper and lower eyelid margins as a result of incomplete separation during embryologic development. Presentation may vary from a few connecting bands to complete fusion of the eyelids. Mild cases in which only a few webs of adherent tissue are present may be treated in the clinician’s office using scissors to cut the aberrant tissue. More extensive intervention is indicated when the eyelid compromises the visual axis and there is concern for the development of amblyopia.
An eyelid coloboma is a cleft or notch in the eyelid. These defects are typically an isolated finding in the upper eyelid. When located in the lower lid, colobomas may be associated with other congenital anomalies, such as Goldenhar syndrome. Infants with an eyelid coloboma are at high risk for the development of exposure keratopathy and often require surgical intervention.
Ectropion is eversion of the eyelid margin. Congenital ectropion is caused by a vertical deficiency of the eyelid’s connective tissue (tarsal plate) or muscle (orbicularis oculi) and occurs more commonly in the lower eyelid. Congenital ectropion only rarely occurs as an isolated finding; more commonly, it is associated with ichthyosis, Down syndrome, or other midface developmental anomalies. In contrast to ectropion, entropion is inversion of the eyelid margin. Congenital entropion does not resolve spontaneously, and intervention is indicated for cases in which the ocular surface is exposed or otherwise compromised by in-turning of the lashes.