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Valeria M. Carvalho, Luis A. Carvalho, Vanderlei S. Bagnato; Development and Preliminary Results of a Chromatic Illumination System for Indirect Ophthalmoscopes. Invest. Ophthalmol. Vis. Sci. 2012;53(14):3095.
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White light, with the option of blue and green filters have long been applied in indirect ophthalmoscopy, but little effort has been done in order to investigate if other wavelengths could bring different and useful information to the visualization and diagnosis of retinal pathologies. Wavelengths situated in the visible light spectra, when used to illuminate biological tissue, usually cause interactions (mainly absorption, scatter and refraction) that alter the spectral composition of the emerging light, thus changing the observed image according to the morphology and optical properties of substances and structures present in the tissue. Based on this principle and recent previous studies of our group using chromatic light applied to other tissues , we present here a new and low-cost chromatic illumination system that may be adapted to virtually any brand of commercial indirect ophthalmoscope.
The original illumination system of a conventional indirect ophthalmoscope was substituted by the new RGB illumination system developed here. This new illumination system was constructed using three independent high power LEDs (1W each) in the colors red, green and blue, and an optical system consisting of different band-pass beam splitters used to mix the different colors. A windows based home-made software and user interface and a micro-controlled hardware were designed in order to control the individual intensities of each LED and therefore generate virtually any desired color of the visual spectrum.
Preliminary tests were conducted on a mechanical eye (Heine Optotechnik, Germany) and an in vivo healthy subject (signed consent according to the Declaration of Helsinki). Images for the mechanical eye and the in vivo subject were captured for various distinct colors and are presented here.
The adaptation of this new illumination hardware does not require extreme modifications to the original setup of the commercial equipment. The images presented here show that the technique of chromatic illumination may be successfully applied to the traditional optical principle of indirect ophthalmoscopy. Our team was surprised to see the differences in contrast of certain elements of the in vivo retina for different colors and our claim is that this innovative, simple and cost-effective technique may improve visual diagnosis of different retinal pathologies and therefore deserves to be shared and further investigated by the scientific community. Barrionuevo WR, Filho EM, Bagnato VS, Enhanced Visualization of Histological Samples With an Adjustable RGB Contrast System With Application for Tissue Used in Photodynamic Therapy, Microsc Res Techniq, v. 71, p. 403-408, 2008.
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