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M.C. Cheney, A.E. Elsner, S.A. Burns, M.B. Kairala, C.L. Trempe, K. Lashkari, J.J. Weiter, M. Miura, M. Osako, M. Usui; Polarization Amplitude and Phase Changes in Retinal Exudation . Invest. Ophthalmol. Vis. Sci. 2003;44(13):5001.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To understand light-tissue interactions in retinal exudation. To investigate novel polarimetry methods for imaging retinal pathology. We hypothesize that by combining polarization data in novel ways, visualization of specific features can be improved. Methods: Maculas of 38 patients were imaged: 27 with advanced Age-Related Macular Degeneration (AMD), 2 younger patients with CNV, and 9 with central serous retinopathy (CSR). Scanning laser polarimetry (GDx, LDT) provided raw image data in 1 sec of 20 image pairs that varied in illumination polarization angle, and simultaneously sampled at crossed and uncrossed polarizations. A depolarized light image was computed from the portion of the light that was unmodulated for each pixel, for the uncrossed detectors. The relative birefringence image was computed from the light that modulated with input polarization, separately for the crossed and uncrossed detectors. Phase plots were computed by finding the phase angle of maximum light return in the crossed and uncrossed detectors. Additional images representing different polarization properties were computed by subtracting polarization-modulated signals from the mean total light returned, and from the mean signal at the uncrossed detector. The equivalent of standard confocal images were also computed. Results: Depolarized light images revealed features distinctly different from those emphasized in the birefringence images, particularly in areas of exudation. Such features include pools of fluid, retinal vascular changes, drusen, and retinal striae. For instance, a pool of fluid was readily visualized in images in which the polarization modulated components were subtracted, which were uniform in gray scale despite overlying and underlying pathology (p=.33 for two regions within the fluid, but p < .0001 for within the fluid vs. adjacent structures). Both sets differed systematically from the standard confocal images. Our data cannot be described by polarization changes due merely to the anterior segment in aged patients, as the phase plots revealed feature-specific deviations from either constant phase or the standard macular bow-tie. Conclusions: Novel methods of analysis of polarimetry data can readily localize components of exudation in macular disease.
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