Kayser–Fleischer rings are deposits of copper, seen as a brownish discoloration, in Descemet’s membrane. Although often visible to the naked eye (difficult in people with a brown iris), they are best seen with slit-lamp examination. Since they are a highly reliable sign of intracerebral copper deposition in Wilson’s disease (hepatolenticular degeneration), any patient suspected of this diagnosis (i.e. with parkinsonism or dystonia presenting before age 50 years) should have a slit-lamp examination (as well as blood copper and caeruloplasmin, and urinary copper, measurements). Very occasionally cases of neurological Wilson’s disease without Kayser–Fleischer rings have been reported.