A 25-year-old man with Type 1 diabetes mellitus experienced rapid visual decline and was scheduled for right cataract surgery. At the time of administering an inferotemporal retrobulbar block, a white discharge appeared spontaneously on the surface of the globe. Superotemporally a cyst was found and its contents were subtotally evacuated. Microscopically, eosinophilic, acellular material with chatter artifact and small vacuoles was detected and initially thought to represent a lens choristoma. This material stained moderately with the periodic acid Schiff method and was focally Congo red positive without apple green birefringence; it also stained blue with the Masson trichrome method. Acid-fast staining disclosed the presence of rare vellous hairs. Adherent cells were not epidermal cells (CK5/6) but conjunctival epithelial cells (CK7); CD68-positive histiocytes were also identified. The lesion was diagnosed as a disrupted orbital dermoid cyst of conjunctival origin.