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In vivo volumetric imaging of human retinal circulation with phase-variance optical coherence tomography.

ABSTRACT: We present in vivo volumetric images of human retinal micro-circulation using Fourier-domain optical coherence tomography (Fd-OCT) with the phase-variance based motion contrast method. Currently fundus fluorescein angiography (FA) is the standard technique in clinical settings for visualizing blood circulation of the retina. High contrast imaging of retinal vasculature is achieved by injection of a fluorescein dye into the systemic circulation. We previously reported phase-variance optical coherence tomography (pvOCT) as an alternative and non-invasive technique to image human retinal capillaries. In contrast to FA, pvOCT allows not only noninvasive visualization of a two-dimensional retinal perfusion map but also volumetric morphology of retinal microvasculature with high sensitivity. In this paper we report high-speed acquisition at 125 kHz A-scans with pvOCT to reduce motion artifacts and increase the scanning area when compared with previous reports. Two scanning schemes with different sampling densities and scanning areas are evaluated to find optimal parameters for high acquisition speed in vivo imaging. In order to evaluate this technique, we compare pvOCT capillary imaging at 3x3 mm(2) and 1.5x1.5 mm(2) with fundus FA for a normal human subject. Additionally, a volumetric view of retinal capillaries and a stitched image acquired with ten 3x3 mm(2) pvOCT sub-volumes are presented. Visualization of retinal vasculature with pvOCT has potential for diagnosis of retinal vascular diseases.

SUBMITTER: Kim DY

PROVIDER: S-EPMC3114219 | biostudies-other | 2011 Jun

REPOSITORIES: biostudies-other

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Project description:PURPOSE:To detect macular perfusion defects in glaucoma using projection-resolved optical coherence tomography (OCT) angiography. DESIGN:Prospective observation study. PARTICIPANTS:A total of 30 perimetric glaucoma and 30 age-matched normal participants were included. METHODS:One eye of each participant was imaged using 6×6-mm macular OCT angiography (OCTA) scan pattern by 70-kHz 840-nm spectral-domain OCT. Flow signal was calculated by the split-spectrum amplitude-decorrelation angiography algorithm. A projection-resolved OCTA (PR-OCTA) algorithm was used to remove flow projection artifacts. Four en face OCTA slabs were analyzed: the superficial vascular complex (SVC), intermediate capillary plexus (ICP), deep capillary plexus (DCP), and all-plexus retina (SVC + ICP + DCP). The vessel density (VD), defined as the percentage area occupied by flow pixels, was calculated from en face OCTA. A novel algorithm was used to adjust the vessel density to compensate for local variations in OCT signal strength. MAIN OUTCOME MEASURES:Macular retinal VD, ganglion cell complex (GCC) thickness, and visual field (VF) sensitivity. RESULTS:Focal capillary dropout could be visualized in the SVC, but not the ICP and DVP, in glaucomatous eyes. In the glaucoma group, the SVC and all-plexus retinal VD (mean ± standard deviation: 47.2%±7.1% and 73.5%±6.6%) were lower than in the normal group (60.5%±4.0% and 83.2%±4.2%, both P < 0.001, t test). The ICP and DCP VD were not significantly lower in the glaucoma group. Among the overall macular VD parameters, the SVC VD had the best diagnostic accuracy as measured by the area under the receiver operating characteristic curve (AROC). The accuracy was even better when the worse hemisphere (inferior or superior) was used, achieving an AROC of 0.983 and a sensitivity of 96.7% at a specificity of 95%. Among the glaucoma participants, the hemispheric SVC VD values were highly correlated with the corresponding GCC thickness and VF sensitivity (P < 0.003). The reflectance compensation step in VD calculation significantly improved repeatability, normal population variation, and correlation with VF and GCC thickness. CONCLUSIONS:On the basis of PR-OCTA, glaucoma preferentially affects perfusion in the SVC in the macula more than the deeper plexuses. Reflectance-compensated SVC VD measurement by PR-OCTA detected glaucoma with high accuracy and could be useful in the clinical evaluation of glaucoma.

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In vivo volumetric imaging of human retinal circulation with phase-variance optical coherence tomography.

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