Unilateral optic disc pit associated with orbital cyst in a child.

Optic disc pit and disc coloboma are common congenital anomalies. Both have been known to be associated with an orbital cyst. We report a case of a 6 month-old child who presented with unilateral progressive proptosis. Imaging investigations revealed a well-defined, intraconal, orbital cyst located close to the posterior surface of the globe displacing the optic nerve laterally. The cyst was excised and histopathological examination showed the cyst to have a lining of glial tissue, a thin epithelial lining, over a layer of collagenous connective tissue matrix. We hypothesize that colobomatous disc abnormalities and optic disc pits are different points on the same disease spectrum and can be associated with orbital cysts. Furthermore, our case points to the possible role of imaging the optic nerve in all cases of optic disc anomalies.