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C.K. Hitzenberger, E. Götzinger, M. Pircher, M. Sticker, A.F. Fercher; Birefringence Properties of Normal Human Cornea Imaged by Phase Resolved Polarization Sensitive Optical Coherence Tomography . Invest. Ophthalmol. Vis. Sci. 2003;44(13):3669.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To measure and image the three-dimensional distribution of birefringence of the normal human cornea. To provide a deeper insight into structures and mechanisms causing corneal birefringence and to establish standard patterns of 3D birefringence distribution. Methods: A phase sensitive polarization sensitive optical coherence tomography (PS-OCT) system was developed that allows measurement and imaging of three tissue parameters simultaneously: reflectivity, retardation, and fast optic axis orientation. This instrument was used to obtain 3D PS-OCT data sets of normal human corneas in vitro. From the 3D data sets, conventional cross sectional, as well as en face sectional images of reflectivity, retardation, and optic axis orientation were derived. Results: Phase retardation increases with tissue depth. In transversal direction the retardation distribution has a radially symmetric shape, retardation is lowest at the center of the cornea and increases towards the periphery. The distribution of the optic axis is not constant with the parallel illumination scheme used. Optic axis orientation is an approximately linear function of azimuth angle, however, if averaged over the entire cornea, a preferential optic axis orientation is observed. Conclusions: The results provide additional insight into corneal birefringence as compared to published work where corneal birefringence is usually averaged over a larger area. The results can be explained by a birefringence model based on stacked collagen fibril lamellae of different orientations. The observed birefringence patterns in normal corneas might be used as standard patterns for comparisons with pathologic changes.
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