Optical Illusions in Clinical Dermatology: The Mach Band Phenomenon and Afterimages

Abstract

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.

Dihydroxyacetone Test as a Substitute for the Dansyl Chloride Test

“…Recently the possibility of percu taneous poisoning has been pointed out [7], This test also proves to be difficult to interpret because it is not easy to clinically evaluate with precision the moment of fluores cence loss. This is due to the uneven fade-out of fluores cence at the skin surface [5,6], the long persistence of fluo rescence in the hair follicle ostia and physiological imper fections in visual assessments [8,9].Searching for a substitute to the dansyl chloride test, we investigated the rate of elimination of the stratum corneum pigmentation induced by dihydroxyacetone (DHA) which is widely used in topical self-tanning preparations. This product transforms colorless compounds of the stratum corneum to brown substances, called melanoids, by the Maillard's reaction occurring when some aldols and ketols react with amino acids [10][11][12][13][14] …”

Dentists Make Larger Holes in Teeth Than They Need to If the Teeth Present a Visual Illusion of Size

“…Again, other health-care practitioners are aware of the importance of illusions for producing a cosmetically pleasing result [22] and in diagnosis or treatment [16], [18], [19], [21], [44], [45]. We chose a model system that bore a close resemblance to the classic Delboeuf illusion, with rigid, near-circular shapes.…”

“…Indeed, visual illusions have been implicated in errors of diagnosis [16], [17], [18], [19], [20], [21] and of treatment [2], [22].…”

“…Although studies have suggested that visual illusions could affect diagnosis [16], [17], [18], [19], [20], [21], we are unaware of any that use simulation to take a prospective approach.…”

Illusion and Reality in Visual Observation: A Trap for the Unwary Clinician

“…In an article appearing in this issue, Wagner ct al. [25] have the merit of drawing the attention of derma tologists to the potential consequences of optical illusions, such as those related to the astonishing Mach band phe nomenon.…”