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E. Gotzinger, B. Baumann, M. Pircher, C. K. Hitzenberger; Polarization Maintaining Fiber Based Ultra-High Resolution Spectral Domain Polarization Sensitive Optical Coherence Tomography of the Human Retina. Invest. Ophthalmol. Vis. Sci. 2010;51(13):1050.
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© ARVO (1962-2015); The Authors (2016-present)
To measure the polarization properties of the foveal and nerve head region with a fiber based ultra high resolution polarization sensitive OCT (PS-OCT) system.
We present a new ultra high resolution spectral domain polarization sensitive optical coherence tomography (PS-OCT) system based on polarization maintaining (PM) fibers. The method transfers the principles of our previous bulk optic PS-OCT systems to a fiberized setup. Thereby, the main advantage of our bulk optics setups, i.e. the use of only a single input polarization state to simultaneously acquire reflectivity, retardation, optic axis orientation, and Stokes vector, is maintained.
We measured the fovea and the nerve head of healthy volunteers with our system. The polarization sensitive images of the macula show, that most of the retinal layers in this area do not alter the polarization state. However, the RPE changes the polarization state of backscattered light in a random way. This polarization scrambling indicates depolarization. The retardation images of the nerve head region show increased retardation in the superior and inferior nerve fiber bundles and decreased retardation in the nasal and temporal nerve fiber layer. The optic axis orientation image shows a 360° rotation around the nerve head, in good agreement with the radial orientation of the nerve fiber bundles around the optic nerve head.
The flexibility and simple alignment of fiber optics based systems is an important step towards the development of commercial PS-OCT systems. In addition the use of a broadband light source with a bandwidth of 110 nm results in a smaller speckle size. This increases the density of independent sampling points, leading to improved resolution of PS measurements, which is especially important for measurements of the thinner part of the retinal nerve fiber layer. In addition, the smaller speckle size allows a better resolution of depolarization measurements, leading to improved spatial resolution of RPE segmentation.
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