Feasibility of Combined Spectral Domain Polarization Sensitive OCT and SLO for Clinical Retinal Imaging

Abstract

Purpose: : To demonstrate the clinical ability of a new polarization-sensitive optical coherence tomography (PS-OCT) device for imaging healthy and diseased retinas. Using PS-OCT, an additional contrast mechanism relying on tissue-specific polarization properties is available.

Methods: : An advanced spectral domain PS-OCT device with a built-in SLO channel was constructed to be employed for retinal imaging. A superluminescence diode (center wavelength 839 nm; bandwidth 58 nm) was used as a light source providing a high axial resolution of 4 µm in tissue. The OCT system operates at an A-line rate of 20 kHz. The incorporated SLO enables fast en-face imaging of the retina with a field of view of 20°. An interleaved SLO/OCT display is provided for alignment of the eye under investigation. Three-dimensional (3D) PS-OCT data sets consisting of either 64, 128 or 256 B-scans (each 1024, 512 or 256 A-scans) can be recorded within 3.3 s. In addition to high resolution intensity images, PS-OCT images displaying polarization parameters (retardation, optic axis orientation, degree of polarization uniformity) were calculated from the 3D data sets.

Results: : 3D PS-OCT data sets were recorded in more than 200 eyes of patients with various retinal diseases. PS-OCT provides additional tissue-specific contrast based on the light polarizing properties of the different retinal structures which can be birefringent, non-polarizing or depolarizing. For instance, Stokes vector analysis enables segmentation of depolarizing tissue like the retinal pigment epithelium (RPE). En-face maps visualizing the location of the depolarizing tissue were generated which allow for monitoring morphological changes in the retina during clinical studies.

Conclusions: : PS-OCT provides unique discrimination of different retinal structures based on their polarizing properties. The new clinical PS-OCT instrument presented here increases image contrast in retinal imaging and might be a powerful tool especially for monitoring effects of treatment.

Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • imaging/image analysis: clinical • optical properties