A coloboma is an embryo logic cleft of uncertain etiology. Eyelid colobomas can occur in either the upper eyelid or lower eyelid. Upper eyelid colobomas are often full thickness and triangular in shape (occasionally quadrilateral or irregular). They are most often found medially and the size can be from a tiny indentation to the full length of the eyelid. They can be unilateral or bilateral. They often cause corneal exposure problems, especially if the defect is greater than one third of the eyelid.
In contrast, lower eyelid colobomas are usually partial thickness (with some remnants of orbicularis, tarsal remnants, cilia, or glandular structures) and rounded. They are found most often laterally and the length can also be from a tiny indentation to the full length of the eyelid. These are found unilaterally or bilaterally. They can also cause corneal exposure problems and often cause trichiasis as well.
Eyelid colobomas occur from delayed or incomplete union of the mesodermal sheaths of the frontonasal and maxillary processes. They are often associated with other ocular, periorbital, or facial defects.
Treatment of eyelid colobomas depends on the status of the cornea. If there is minimal or no damage to the cornea, medical treatment with drops or ointments is indicated with elective surgery during the first four years of life. If moderate damage is present, medical treatment with drops and ointments is indicated with possible use of soft contact lenses and moisture chambers. Close follow-up is essential. If the eye responds favorably, then elective surgery can be performed during the first four years of life. However, if the corneal problems persist, reconstructive surgery should be performed sooner. Finally, if severe corneal damage is present, the above temporizing measures should take place until surgery can be performed. Since surgery is easier to perform when the patient is older, due to increased laxity of the surrounding tissues, surgery should be delayed until it is either necessary or there is enough laxity of the surrounding tissues.