Choristomas represent congenital overgrowth of normal tissues in an abnormal location. The simultaneous presence of epibulbar choristoma and microphthalmos has rarely been reported. The authors report a case of extensive epibulbar choristoma associated with microphthalmos.

A 9-day-old boy with the left eyeball absent from birth was referred to our clinic. A large cornea-like structure covered by keratinized membrane was observed inside the eyelid aperture, therefore buphthalmos or corneal staphyloma with microphthalmos was presumed. At the age of 2 months, a large mass of central conjunctival sac protruded through the left eyelid aperture. Manual reduction could not return the tissue to its original site and the mass immediately protruded again. At the age of 9 months, orbital magnetic resonance imaging showed the small presumed ocular tissue behind the large mass of fat signal in the central anterior orbit, therefore, extensive epibulbar choristoma associated with microphthalmos was diagnosed. At 12 months of age, partial excision of the protruding portion of the mass was performed. Based on pathologic examination, the mass was determined to be a choristoma and cosmetically acceptable appearance with prosthesis was maintained for 10 months after the surgery.

Because there is no vision in extensive choristoma associated with microphthalmos, the treatment goal is cosmetic improvement. Conjunctivoplasty following partial mass excision for prosthesis wearing is a good treatment option.