Evaluation of congenital optic disc pits and optic disc colobomas by swept-source optical coherence tomography

Purpose. To investigate the structural abnormalities of optic disc pits and colobomas by swept- source optical coherence tomography (OCT). Methods. Sixteen eyes with congenital optic disc pits, and seven eyes with optic disc colobomas were studied. Papillary and peripapillary areas were examined with swept-source OCT. The entire course of the pit or cavity and the spatial relationship between pits and retrobulbar subarachnoid space (SAS) were examined. RESULTS. Optical coherence tomography images showed the entire course of the pits from their openings to the bottom in 12 eyes. Shape of optic disc pits varied from sharp triangular cavities to longitudinally oval according to the depth of the pits. In the other four eyes, the pit narrowed into a tunnel along the optic nerve. The entire area of the optic disc was observed in three of seven eyes with disc coloboma by OCT. In all of the eyes with optic disc pits, the lamina cribrosa was torn off of the peripapillary sclera at the site of the pits. In two cases with optic disc pits and one case with optic disc coloboma, Optical coherence tomography showed SAS immediately posterior to the highly reflective tissue lining the bottom of the excavation. The distance between the intraocular cavity and SAS in these three cases were 88, 126, and 133 μm. CONCLUSIONS. Swept-source OCT is able to detect different kinds of abnormalities including shape of cavities, defect of lamina cribrosa, or distance to SAS in the excavated optic discs anomalies.