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May 2002

A False Use of "True Color"

Author Affiliations

Copyright 2002 American Medical Association. All Rights Reserved. Applicable FARS/DFARS Restrictions Apply to Government Use.2002

Arch Ophthalmol. 2002;120(5):675-676. doi:

We read with great interest the article by Manivannan et al1 on the clinical investigation of a color scanning laser ophthalmoscope. The use of the term "true color" is scientifically incorrect and may be confusing for readers. It is a well-established principle of physics that a laser light source has only a single wavelength. The authors have developed an instrument that has 3 wavelengths of light (blue, 488 nm; green, 532 nm; and red, 670 nm). Each laser emits a very narrow spectrum of light, and the authors combined all 3 lasers to yield the appearance of white light. The spectrum of the light is, however, not continuous. Only 3 discrete sections of the spectrum are present. There is no interaction among the 3 colors. If one were to view the blue and green lights mixed, they would appear to be yellow light. The retina, however, will not reflect the yellow illumination light. It will reflect blue light and green light separately.

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