Which of the following is NOT listed as a cause of brown corneas?

• A. Desmetocoele
• B. Iris prolapse
• C. Foreign body
• D. Cataract

Answer: (D)

Brown corneas arise from anterior segment problems that introduce pigment or staining onto the cornea. Desmetocele reflects a deep corneal ulcer with Descemet's membrane involvement, and the resulting defect can be pigmented or stained, giving a brown appearance. Iris prolapse brings iris tissue into or through a corneal defect, often with pigment from the iris contributing to the brown look. A foreign body in the cornea can cause staining—such as rust staining from iron—leading to brown discoloration.

Cataract, however, is a lens pathology. It causes opacity within the lens and does not color the cornea itself. Therefore cataract is not listed as a cause of brown corneas.