Abstract
We developed a method based on polarization-sensitive optical coherence tomography (PS-OCT) to quantify the double pass phase retardation (DPPR) induced by Henle fiber layer in three subjects. Measurements of the retina were performed at a mean wavelength of 840 nm using two polarization states that were perpendicular in a Poincaré sphere representation and phase retardation contributions from tissue layers above and below the Henle fiber layer were excluded using appropriately placed reference and measurement points. These points were semi-automatically segmented from intensity data. Using a new algorithm to determine DPPR, the Henle fiber layer in three healthy subjects aged 50-60 years showed elevated DPPR in a concentric ring about the fovea, with an average maximum DPPR for the three subjects of 22.0° (range: 20.4° to 23.0°) occurring at an average retinal eccentricity of 1.8° (range: 1.5° to 2.25°). Outside the ring, a floor of approximately 6.8° was measured, which we show can mainly be attributed to phase noise that is induced in the polarization states. We also demonstrate the method can determine fast axis orientation of the retardation, which is found consistent with the known radial pattern of Henle fibers.
Highlights
The structured organization of the Henle fiber layer (HFL) is well known to exhibit birefringence, a difference in refractive index experienced by light polarized perpendicular and parallel to the direction of the fibers [1]
We have developed a method based on polarization-sensitive optical coherence tomography (PS-OCT) to measure the retardation induced by HFL
While this study focused on measuring the magnitude of the HFL phase retardation, measuring its orientation is possible with the presented PS-OCT method
Summary
The structured organization of the Henle fiber layer (HFL) is well known to exhibit birefringence, a difference in refractive index experienced by light polarized perpendicular and parallel to the direction of the fibers [1]. Since disruption indicates structural changes to otherwise well-ordered neural tissues, birefringence measurements may serve as a sensitive indicator of disease onset To investigate these possibilities, we have developed a method based on polarization-sensitive optical coherence tomography (PS-OCT) to measure the retardation induced by HFL. Using an open air PS-OCT system without single mode fiber and an input state that was circularly polarized, Götzinger et al determined the birefringence induced by the RNFL by fitting DPPR data with a linear regression method [13]. They used a histogram of DPPR data obtained near the photoreceptors to determine the maximum DPPR induced by the RNFL. A reference measurement is acquired above HFL (below the RNFL), while the retardation induced by the HFL is recorded at the interface between the inner and outer segments of the photoreceptor layer
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