Map-dot-fingerprint type corneal dystrophy is a condition where the cornea, the normally transparent front part of the eye, displays map-like lines, dots or microcysts, and gray fingerprint-like patterns when examined with a slit-lamp. This instrument uses a high-intensity light beam to illuminate the eye while the examiner views it through a magnifying scope. Typically, this condition does not cause symptoms, but about 10% of individuals may experience corneal erosion, often starting after the age of 30. Interestingly, half of those with recurrent corneal erosions of unknown cause are found to have this condition. The disorder involves abnormalities in the epithelial basement membrane, leading to its alternative name, epithelial basement membrane corneal dystrophy. First described by Cogan and colleagues in 1964, it is sometimes referred to as Cogan corneal dystrophy, and it is also known as microcystic corneal dystrophy.