They are due to copper deposition in the Descemet's membrane as a result of particular liver diseases.

Eventually, a second crescent forms below, at the "six o'clock position", and ultimately completely encircles the cornea.

[1][6] Kayser–Fleischer rings are a sign of Wilson's disease, which involves abnormal copper handling by the liver resulting in copper accumulation in the body and is characterised by abnormalities of the basal ganglia of the brain, liver cirrhosis, splenomegaly, involuntary movements, muscle rigidity, psychiatric disturbances, dystonia and dysphagia.

The combination of neurological symptoms, a low blood ceruloplasmin level and KF rings is diagnostic of Wilson's disease.

In certain situations, they are actively sought; in that case, the early stages may be detected by slit lamp examination before they become visible to the naked eye.