Abstract
In phase-resolved OCT angiography blood flow is detected from phase changes in between A-scans that are obtained from the same location. In ophthalmology, this technique is vulnerable to eye motion. We address this problem by combining inter-B-scan phase-resolved OCT angiography with real-time eye tracking. A tracking scanning laser ophthalmoscope (TSLO) at 840 nm provided eye tracking functionality and was combined with a phase-stabilized optical frequency domain imaging (OFDI) system at 1040 nm. Real-time eye tracking corrected eye drift and prevented discontinuity artifacts from (micro)saccadic eye motion in OCT angiograms. This improved the OCT spot stability on the retina and consequently reduced the phase-noise, thereby enabling the detection of slower blood flows by extending the inter-B-scan time interval. In addition, eye tracking enabled the easy compounding of multiple data sets from the fovea of a healthy volunteer to create high-quality eye motion artifact-free angiograms. High-quality images are presented of two distinct layers of vasculature in the retina and the dense vasculature of the choroid. Additionally we present, for the first time, a phase-resolved OCT angiogram of the mesh-like network of the choriocapillaris containing typical pore openings.
Highlights
Introduction and theoryAngiography is routinely used in ophthalmology for the assessment of the retinal and choroidal circulation and has become essential in the diagnosis of ocular pathology
In optical coherence tomography (OCT) angiography blood flow is discriminated from static tissues by analyzing phase changes [11,12,14,15] or intensity changes [16,17] in the OCT signal that are caused by moving lightscattering particles
In this paper we present eye-motion-corrected inter-B-scan phase-resolved OCT angiography using a phase-stabilized optical frequency domain imaging (OFDI) system combined with experimental real-time tracking scanning laser ophthalmoscope (SLO) (TSLO)
Summary
Angiography is routinely used in ophthalmology for the assessment of the retinal and choroidal circulation and has become essential in the diagnosis of ocular pathology. A high phase-noise due to a low SNRs or a high Δx/d ratio results in a high vmin and makes the detection of blood flow more difficult This restricts any spot displacement to be within a small fraction of the spot size for good quality angiograms. In this paper we present eye-motion-corrected inter-B-scan phase-resolved OCT angiography using a phase-stabilized optical frequency domain imaging (OFDI) system combined with experimental real-time tracking SLO (TSLO). It was shown previously that the combined OFDI-TSLO setup was able to significantly reduce the amount of eye motion artifacts in OCT intensity imaging of retinal structures and the optic nerve head [31] Using this setup we show, to our knowledge, for the first time how eye tracking reduces artifacts in phase-resolved OCT angiograms and analyze its performance with respect to the spot stability on the retina. High-quality images are presented of two distinct layers of vasculature in the retina, the dense vasculature of the choroid, and the mesh-like network of the choriocapillaris
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