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B. Povazay, B. Hermann, V. Kajic, B. Hofer, W. Drexler; Three-Dimensional, High Resolution Optical Coherence Tomography at 1050 nm With 74 Frames/s for Extension of the Imaging Range to the Choroidal-Scleral Interface. Invest. Ophthalmol. Vis. Sci. 2008;49(13):1849. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To exploit the advantages of high speed, high resolution optical coherence tomography (OCT) at longer wavelengths (1050 nm) for retinal and choroidal imaging, with focus on the intraocular layer structure and its vasculature, including the choroidal-scleral interface.
A novel high speed 3D-OCT system was developed, capable to utilize >70 nm spectral bandwidth, corresponding to ~7 µm effective axial resolution on a specially designed InGaAs camera and could be operated at 50k depth-scans/s to acquire ~120 Mvoxel tomograms (74 frames/s with 512 depth-scans per frame) of the retina and the choroid of human subjects in less than 5 seconds. Remaining motion artifacts could be significantly reduced by introduction of rigid body transform and warping techniques.
Isotropic (equidistant in all directions) OCT sampling of the retina allows reconstruction of retinal and choroidal microvasculature, revealing its three interconnected meshworks simultaneously with visualization of the three layers of the choroid, solely on vessel reflectivity, without use of contrast agents in vivo. Three-dimensional vascular architecture can be visualized even at low eccentricities at the fovea (0.7°, i.e.~0.2 mm) in the ganglion cell layer, the inner and outer nuclear layer to form the avascular zone. The fine structure of the choriocapillaris, Sattler’s and Haller’s layer can be differentiated and the choroidal/scleral interface was clearly visualized allowing continuous segmentation of choroidal thickness for the first time. Large angle field scans (up to 30°x30°) unveil the complete retinal and choroidal vascular meshwork and allow insight into the retinal blood support. At the optic nerve head deeper penetration and high sampling density improves access to the 3D fine structure of the lamina cribrosa.
OCT at 1050 nm significantly profits from the lower scattering and might therefore provide superior clinical feasibility compared to the commonly used 800 nm devices. Aside from improved imaging performance in cataract eyes enhanced penetration allows an unprecedented combination of high speed imaging, high transversal and axial resolution at sufficiently high sampling rates to give access to fine morphological details in the retina and the choroid, necessary for early diagnosis of diabetic retinopathy, age related macular degeneration and glaucoma.
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