The presence or absence of melanocytes in the human optic nerve and its meningeal sheaths.
D006801:Humans; D008544:Melanocytes / Q000166:cytology*; D008578:Meninges / Q000166:cytology*; D008581:Meningitis / Q000473:pathology; D009900:Optic Nerve / Q000166:cytology*; D009902:Optic Neuritis / Q000473:pathology; D014605:Uveitis / Q000473:pathology