Investigations on retinal vasculature and blood flow are of interest for understanding and diagnostics of numerous ocular diseases. Conventional OCT systems use various scan patterns like linear B-scans, circular scans around the optic nerve head, or raster scans for 3D data acquisition. However, for some studies it is preferable to have customized scan patterns that can, e.g., follow the trace of an arbitrary linear structure in the retina, such as a vessel. In this work, we present an OCT instrument with an integrated retinal tracker that allows repeated scans along an arbitrary trace, whereby ocular motions are corrected by the retinal tracker. The setup comprises an OCT system and a line scanning laser ophthalmoscope (LSLO). The OCT subsystem operates at a center wavelength of 860 nm, with a bandwidth of 60 nm and an A-scan rate of 70kHz. The LSLO system operates at 790 nm and at a frame rate of 60 Hz. This system was used for reflectivity and Doppler imaging along retinal vessels. In a first step, the vessel is manually marked on the LSLO image. Then, repeated scans along the vessel trace are performed (2048 A-scans per scan along trace, up to 500 scans along the trace). The intensity images show a clear delineation of the vessel walls, the phase difference (Doppler) tomograms allow for a time-resolved analysis of blood flow along the vessel over the cardiac cycle.
Measurement and imaging of depolarization by polarization-sensitive optical coherence tomography (PS-OCT) requires averaging of Stokes vector elements within two- or three-dimensional (3-D) evaluation windows to obtain the degree of polarization uniformity (DOPU). By use of a PS-OCT system with an integrated retinal tracker, we analyze optimum conditions for depolarization imaging, data processing, and segmentation of depolarizing tissue in the human retina. The trade-offs between figures of merit like DOPU imaging sensitivity, efficiency, and susceptibility are evaluated in terms of 3-D resolution. The results are used for a new, detailed interpretation of PS-OCT high-resolution images of the human retinal pigment epithelium and Bruch’s membrane.