Uveal melanoma: case report of extension through the optic nerve to the surgical margin in the orbital apex.

An unsuspected uveal melanoma arising in a phthisical eye extended through the optic nerve to the surgical margin in the orbital apex without involvement of other orbital structures. Step sections showed the continuous extension through the nerve. Factors likely to predispose to optic nerve extension include epithelioid cell type, large tumour size, peripapillary involvement, and glaucoma. Optic nerve extension carries the risks noted with orbital extension of intraocular tumour, but may in addition lead more directly to intracranial invasion, including a chiasmal syndrome. The role of exenteration and radiotherapy in these cases remains uncertain.