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Peter Ewen King-Smith, Kathleen S Reuter, Carolyn G Begley, Richard J Braun; High Resolution Color Micrographs and Analysis of Tear Film Breakup. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):2499.
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© ARVO (1962-2015); The Authors (2016-present)
To study and analyze high resolution color micrographs of non-invasive tear film breakup.
Over 10,000 high resolution color micrographs from 126 subjects were examined for signs of tear film breakup. Images covered an area of 200 μm diameter with a resolution of 1 μm. Blur from movement was eliminated by stroboscopic illumination. As described in the results and figures, breakup was recognized as an area bounded by low contrast, colored, contour-like fringes corresponding to the surrounding tear film. Breakup was observed in six subjects. To emphasize these colored fringes, “chromaticity images” were generated to show color information after discarding the luminance information from the lipid layer. Contrast of the recorded and chromaticity images was increased to show details.
Figs. 1 and 2 give examples of high resolution images of breakup; panels A and B show the recorded and chromaticity images. In both figures, the regions of breakup have a pale orange-red color compared to the surrounding tear film. Fig. 1B shows a breakup area (between arrows) of about 50 μm diameter with additional breakup areas at the edge of the image. In Fig. 1A, the reflectance over the breakup areas is similar to that over the tear film whereas the breakup area has high reflectance in Fig. 2A.
The orange color of breakup may be due to interference between reflections from the peaks and valleys of the of the tear surface as it is “draped” over the rough surface of the epithelium. Fluid dynamics simulations indicate that localized evaporation could cause the large breakup area in Fig. 2 but not the smaller area in Fig. 1B. In the latter case, circular objects (perhaps lipid droplets), indicated by arrows in Fig. 1A, may contribute to breakup. In Fig. 2A, arrows indicate dark areas which may be gaps between epithelial cells caused by osmotic shrinkage. The high reflectance in Fig. 2A may be caused by increased refractive index of the ocular surface, again due to osmotic shrinkage.
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