This patient has a melanocytoma, which is a benign melanocytic tumor intrinsic to the optic nerve.
They are intensely pigmented with feathery margins, sometimes spreading into the adjacent retina and choroid.
Learning Points:
Although melanocytomas may enlarge over time, malignant transformation is very rare. Spontaneous necrosis may cause a similar appearance to vitreous seeding from a melanoma.
Vision and visual field loss can rarely occur from compressive optic neuropathy.

