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C. K. Hitzenberger, B. Baumann, E. Götzinger, M. Pircher, C. Ahlers, C. Schuetze, W. Geitzenauer, U. Schmidt-Erfurth; Degree of Polarization Uniformity - A New Intrinsic Tissue Specific Parameter for Characterizing RPE Disease by Polarization Sensitive OCT. Invest. Ophthalmol. Vis. Sci. 2009;50(13):1385.
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© ARVO (1962-2015); The Authors (2016-present)
To introduce a new parameter, the degree of polarization uniformity (DOPU), that can be used for characterization, identification, and segmentation of retinal tissues in polarization sensitive optical coherence tomography (PS-OCT) images.
A new spectral domain PS-OCT system with an integrated SLO channel was developed that allows to simultaneously record 2- and 3-dimensional data sets of backscattered intensity and various polarization parameters in the human retina. Based on Stokes vector analysis, retardation, optic axis orientation, and depolarization can be measured. We previously reported that the retinal pigment epithelium (RPE) scrambles the polarization state of backscattered light, i.e. acts as a depolarizing layer, and used statistical analysis of retardation data to segment the RPE. We now define a new parameter that uses the full information contained in Stokes vectors, DOPU, and apply it for imaging, identification, and segmentation of the RPE. DOPU is related to the classical degree of polarization (DOP, which cannot directly be measured by PS-OCT) by spatial averaging of individual Stokes vector elements. Several healthy eyes and more than 200 eyes with various retinal diseases were imaged.
Most retinal layers show high DOPU values (0.85 -1), indicating that they maintain a high degree of polarization of backscattered light. The RPE strongly depolarizes backscattered light (DOPU 0.3 - 0.5). Similar effects can be found in intraretinal exudates, choroidal naevi, and hyper reflective tissue associated with teleangiectasia and pseudovitelliform dystrophy. RPE segmentation based on DOPU is more reliable than that based on retardation images in areas influenced by birefringence.
The new PS-OCT contrast parameter DOPU provides tissue specific polarization contrast and can be used to identify and segment specific target structures such as RPE selectively based on its depolarizing effect. PS-OCT might improve diagnosis and precise follow-up of RPE-related diseases.
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