Optical illusions in clinical dermatology: the Mach band phenomenon and afterimages.

A survey of dermatologists was conducted to determine whether the perceptions of afterimages and Mach bands impacted on clinical dermatology practice. 26.5% (13/49) of respondents indicated that they perceived one or both of these optical illusions. No false-positive potassium hydroxide interpretations of skin scrapings for hyphae were reported due to perceived afterimages, and no skin biopsies were reportedly performed as a result of Mach bands.