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Shuichi Makita, Masahiro Miura, Shinnosuke Azuma, Toshihiro Mino, Tatsuo Yamaguchi, Yoshiaki Yasuno; High-dense, wide field-of-view, three-dimensional posterior eye imaging by Lissajous scan optical coherence tomography. Invest. Ophthalmol. Vis. Sci. 2021;62(11):11.
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Optical coherence tomography (OCT) is a high-spatial-resolution and three-dimensional imaging modality of microstructure. However, its field of view (FOV) is limited due to involuntary eye movements and restricted imaging speed. We have developed a slowly-shifted Lissajous scan OCT method, which extends FOV with high-densely spatial sampling.
A custom-made 1.0-µm swept-source OCT device with a scan speed of 100,000 A-line/s is used. The OCT probe beam scans along a modified Lissajous pattern, which is designed for both OCT and OCTA. During the scanning, the center of the Lissajous pattern was slightly shifted along a circle pattern. The continuous shifting extends the FOV. The data is subdivided and small regions that overlap each other are registered to estimate eye movements. Motion-free three-dimensional volumes and en face maps of OCT images were created by using the estimated motion amounts.Five eyes of 5 subjects with retinal abnormalities were scanned. The scanning range exceeded around 22.5-degree in diameter. After motion correction, data are remapped in 812 x 812 grid points where the spacing is around 8.4 µm.
Figure 1 shows motion-corrected en face projections and cross-sections of OCT and OCTA images of a representative case of en eye without abnormalities (73 yo, female). The en-face OCTA projection visualizes the retinal vasculature, including capillaries, over an imaging range of 22.5 degrees FOV. Arbitrary cross-sections can be extracted from motion-corrected volumes.Images obtained from a diabetic maculopathy patient (85 yo, male) are shown in Figure 2. Retinal vasculature down to capillary is also visualized in en face OCTA. Re-sliced cross-sections along abnormal blood flow signals indicate hyper-scattering spots associated with blood flow signals. Their distributions are shown in re-sliced en face images.In 5 of 5 eyes with abnormalities, motion-corrected images do not exhibit significant discontinuity of retinal vasculature.
We have shown that high-dense, three-dimensional posterior eye imaging with extended FOV is possible by the Lissajous scan OCT with a slow circular shift.
This is a 2021 Imaging in the Eye Conference abstract.
Motion-corrected en face projections and cross-sections obtained from motion-corrected OCT and OCTA volumes.
En face images and cross-sections obtained from motion-corrected OCT and OCTA volumes of a diabetic maculopathy.
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