Two concepts for ultra-high-resolution polarization-sensitive optical coherence tomography with a single camera

Area of Science:

• Ophthalmology
• Biomedical Optics
• Medical Imaging

Background:

• Spectral-domain optical coherence tomography (SD-OCT) is a key imaging modality in ophthalmology.
• Polarization-sensitive OCT (PS-OCT) adds birefringence information, enhancing diagnostic capabilities.
• Ultra-high resolution (UHR) is critical for imaging thin retinal structures.

Purpose of the Study:

• To introduce and evaluate two novel designs for UHR-PS-OCT systems.
• To assess the performance of these systems in measuring retinal birefringence.
• To demonstrate the utility of UHR-PS-OCT in characterizing retinal pathologies.

Main Methods:

• Development of two UHR-PS-OCT designs utilizing multiplexed superluminescent diodes.
• Design 1: Wollaston prism for separating polarization states onto a single linescan camera.
• Design 2: Beam displacer for separating polarization states onto two lines of a multi-row linescan camera.

Main Results:

• Measured coherence lengths of 3.6 µm and 2.9 µm (n=1.38) for the two designs.
• Successful volumetric scans of healthy subjects, subjects with astigmatism, and a patient with central serous retinopathy (CSR).
• Quantification of retinal nerve fiber layer (RNFL) and Henle fiber layer birefringence, and retinal pigment epithelium-Bruch's membrane complex retardance.

Conclusions:

• The UHR-PS-OCT systems provide high axial resolution for imaging thin retinal tissues like the RNFL.
• Birefringence values of approximately 1°/µm were found in the foveal RNFL.
• Retinal tilting, due to CSR or off-axis imaging, can artificially inflate RNFL and Henle fiber layer birefringence measurements.