Fleischer rings are pigmented rings in the peripheral cornea, resulting from iron deposition in basal epithelial cells, in the form of hemosiderin. They are usually yellowish to dark-brown, and may be complete or broken.
They are named for Bruno Fleischer.
Fleischer rings are indicative of keratoconus, a degenerative corneal condition that causes the cornea to thin and change to a conic shape.
Confusion with Kayser-Fleischer rings
Some confusion exists between Fleischer rings and Kayser-Fleischer rings. Kayser-Fleischer rings are caused by copper deposits, and are indicative of Wilson's disease, whereas Fleischer rings are caused by iron deposits. One example of a medical condition that can present with Fleischer rings is Keratoconus.
References
Fleischer ring Wikipedia(Text) CC BY-SA