Using the dynamic forward scattering signal for optical coherence tomography based blood flow quantification.

To our knowledge, all existing optical coherence tomography approaches for quantifying blood flow, whether Doppler-based or decorrelation-based, analyze light that is back-scattered by moving red blood cells (RBCs). This work investigates the potential advantages of basing these measurements on light that is forward-scattered by RBCs, i.e., by looking at the signals back-scattered from below the vessel. We show experimentally that flowmetry based on forward-scattering is insensitive to vessel orientation for vessels that are approximately orthogonal to the imaging beam. We further provide proof-of-principle demonstrations of dynamic forward-scattering (DFS) flowmetry in human retinal and choroidal vessels.

Predicting subjective refraction with dynamic retinal image quality analysis.

The aim of this work is to evaluate the performance of a novel algorithm that combines dynamic wavefront aberrometry data and descriptors of the retinal image quality from objective autorefractor measurements to predict subjective refraction. We conducted a retrospective study of the prediction accuracy and precision of the novel algorithm compared to standard search-based retinal image quality optimization algorithms. Dynamic measurements from 34 adult patients were taken with a handheld wavefront autorefractor and static data was obtained with a high-end desktop wavefront aberrometer. The search-based algorithms did not significantly improve the results of the desktop system, while the dynamic approach was able to simultaneously reduce the standard deviation (up to a 15% for reduction of spherical equivalent power) and the mean bias error of the predictions (up to 80% reduction of spherical equivalent power) for the handheld aberrometer. These results suggest that dynamic retinal image analysis can substantially improve the accuracy and precision of the portable wavefront autorefractor relative to subjective refraction.

Demonstration of Triband Multi-Focal Imaging with Optical Coherence Tomography.

We demonstrate an extended depth of focus optical coherence tomography (OCT) system based on the use of chromatic aberration to create displaced focal planes in the sample. The system uses a wavelength-swept source tuning over three spectral bands and three separate interferometers, each of which interfaces to a single illumination/collection fiber. The resulting three imaged volumes are merged in post-processing to generate an image with a larger depth of focus than is obtained from each band individually. The improvements are demonstrated in structural imaging of a porous phantom and a lipid-cleared murine brain, and by angiographic imaging of human skin. By using a coaxial approach with Gaussian beams, this approach enables an extended focus with relatively simple microscope optics and data-merging algorithms.