Contralateral blindness from chiasmal extension of unsuspected choroidal melanoma

An 80-year-old woman with a prior diagnosis of age-related macular degeneration in her left eye had rapidly progressive visual loss in her right eye. Orbital MRI revealed a mass involving the left optic nerve and chiasm, interpreted by a radiologist as optic nerve sheath meningioma. Further review of the MRI revealed a mass inside the left eye, characteristic of choroidal melanoma, with apparent extension through the optic nerve to the chiasm and adjacent tissues. Orbital biopsy revealed mixed cell-type melanoma. This case demonstrates that unsuspected choroidal melanoma can invade the optic nerve and chiasm, causing contralateral visual loss. Contralateral blindness as the initial complaint from an unsuspected choroidal melanoma is extremely unusual if not unique.