Five eyes of four patients were studied to analyze the structure of the inner wall of optic and chorioretinal colobomas using swept-source optical coherence tomography (SS-OCT). The colobomatous cavities and their relationship with adjacent structures were examined. SS-OCT permitted the study of the colobomatous cavities in all cases. In four of those cases, a Y-shaped intercalary membrane (ICM) was identified, with an origin in the retinal nerve fiber layer (RNFL), which covered the coloboma and in one case the coloboma was in contact with the vitreous cavity. Vitreous adhesion to the internal wall of the coloboma was found in three cases. No clinical or tomographic maculopathy was observed in any patient. High-resolution deep penetration SS-OCT allows in vivo study of optic and chorioretinal colobomas, identifying the RNFL as the main component of the ICM overlying the colobomatous cavities.

In patients with genetically heterogeneous disorders such as intellectual disability or epilepsy, exome sequencing is a powerful tool to elucidate the underlying genetic cause. Homozygous and compound heterozygous mutations in C12orf57 have recently been described to cause an autosomal recessive syndromic form of intellectual disability, including agenesis/hypoplasia of the corpus callosum, optic coloboma, and intractable seizures. Here, we report on two siblings from nonconsanguineous parents harboring two compound heterozygous loss-of-function mutations in C12orf57 identified by exome sequencing, including a novel nonsense mutation, and review the patients described in the literature.