Abstract
This paper presents a successful combination of ultra-high speed (120,000 depth scans/s), ultra-high resolution optical coherence tomography with adaptive optics and an achromatizing lens for compensation of monochromatic and longitudinal chromatic ocular aberrations, respectively, allowing for non-invasive volumetric imaging in normal and pathologic human retinas at cellular resolution. The capability of this imaging system is demonstrated here through preliminary studies by probing cellular intraretinal structures that have not been accessible so far with in vivo, non-invasive, label-free imaging techniques, including pigment epithelial cells, micro-vasculature of the choriocapillaris, single nerve fibre bundles and collagenous plates of the lamina cribrosa in the optic nerve head. In addition, the volumetric extent of cone loss in two colour-blinds could be quantified for the first time. This novel technique provides opportunities to enhance the understanding of retinal pathogenesis and early diagnosis of retinal diseases.
Highlights
Optical coherence tomography (OCT) has emerged as a leading technique in ophthalmic imaging due to its capability to non-invasively resolve tissue morphology with high sensitivity and high axial resolution [1,2,3,4,5,6,7,8,9]
Despite increases in axial resolution, monochromatic ocular aberrations [10,11,12] limited the transverse resolution for retinal imaging to ~20 μm, which is too large for visualization of cellular structures
It had previously been shown [22] that increasing the image acquisition speed to 75,000 depth scans/s can improve visualization of retinal features in Adaptive optics (AO)-OCT with longitudinal chromatic aberrations (LCA) correction
Summary
Optical coherence tomography (OCT) has emerged as a leading technique in ophthalmic imaging due to its capability to non-invasively resolve tissue morphology with high sensitivity and high axial resolution [1,2,3,4,5,6,7,8,9]. An achromatizing lens [34] was designed [35,36] to compensate for this effect, and when combined with AO, leads to an appreciable increase in image contrast and both lateral and axial resolution [26,27,29,30,31] It had previously been shown [22] that increasing the image acquisition speed to 75,000 depth scans/s can improve visualization of retinal features in AO-OCT with LCA correction. Considerable technological advances have pushed the imaging potential of OCT further with acquisition speeds reaching up to 106,382 depth scans/s and 312,500 depth scans/s [37] with ~2 μm and ~9 μm axial resolution (without AO for both cases), resulting in a significant reduction in motion artefacts Despite such improvements, it has been shown [31] that saccades of up to ~360 °/s [38] can severely hinder image quality by disrupting volumetric images with motion artefacts in the form of discontinuities. This effect is most critical for AO-OCT since such artefacts can thwart any benefit from AO
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