Congenital coloboma involving the inner third of the upper eyelid is not an uncommon anomaly, particularly if it occurs unilaterally. Less often, however, is the defect noted to contain a bridge of skin intimately adherent to the sclera and cornea of the underlying globe, with absence of the upper canaliculus and apparent lack of a caruncle on the affected side.*
Pathogenesis of so complex a defect is logically attributed to the occurence of an amniotic band (whose remnant is the cutaneocorneal bridge), strangulating mechanically the development of structures normally present in the colobomatous area. This explanation seems not inconsistent with the opinion of Seefelder † that localized failure of adhesion of the lid folds, normally complete in the 35 mm. embryo, results in localized absence of lid margin structures. Of necessity, the amniotic band must be operative prior to the 35 mm. stage.
In a case of bilateral congenital coloboma
SINGER RR. Eyelid Coloboma with Cutaneocorneal Bridge. AMA Arch Ophthalmol. 1956;56(3):449-450. doi:10.1001/archopht.1956.00930040457012