In vivo imaging of the human cornea with high-speed and high-resolution Fourier-domain full-field optical coherence tomography

Abstract

Corneal evaluation in ophthalmology necessitates cellular-resolution and fast imaging techniques allowing accurate diagnoses. Currently, the fastest volumetric imaging technique is Fourier-domain full-field optical coherence tomography (FD-FF-OCT) that uses a fast camera and a rapidly tunable laser source. Here, we demonstrate high-resolution, highspeed, non-contact corneal volumetric imaging in vivo with FD-FF-OCT that can acquire a single 3D volume with a voxel rate of 7.8 GHz. The spatial coherence of the laser source was suppressed to prevent it from focusing to a spot on the retina, and therefore, exceeding the maximum permissible exposure (MPE). Inherently volumetric nature of FD-FF-OCT data enabled flattening of curved corneal layers. Acquired FD-FF-OCT images revealed corneal cellular structures, such as epithelium, stroma and endothelium, as well as subbasal and midstromal nerves.

In vivo dual-mode full-field optical coherence tomography for differentiation of types of melanocytic nevi

“…20 However, as compared to one-dimensional scanning, higher en face rates can be achieved by FF-OCT with two-dimensional (2D) parallel detection owing to the commercially available 2D image sensors with high pixel rates. 22,23 In addition, an FF-OCT that utilizes a 2D camera can address speckle noise because of spatial compounding. 24 In this study, we used a high-brightness light source from Ti:sapphire crystal fiber that provides broadband emission for FF-OCT imaging.…”

Curved-field optical coherence tomography: large-field imaging of human corneal cells and nerves

“…The in-focus FOV, presently limited to 0.85 mm, can be greatly extended by utilizing microscope objectives with smaller NA. For example, reduction in NA from 0.3 to 0.2 will increase the depth of focus by more than twice, while the reduced lateral resolution from 1.7 µm to 2.5 µm will still be sufficient to resolve nerves and cells, as was confirmed in [5,9].…”

“…Emerging in vivo research devices originating from the conventional Fourier-domain optical coherence tomography (OCT), such as UHR-OCT [5,6], GDOCM [7], and µOCT [8] can increase the FOV up to about 1 mm, however, the cellular mosaics on that scale are free of motion artifacts only in anaesthetized animals, immobilized during the prolonged laser beam scanning in the en face plane. The faster corneal Fourier-domain full-field optical coherence tomography (FD-FF-OCT) modality by Auksorius et al [9] can capture images free of scanning-related artifacts with 0.615 mm FOV, but requires costly hardware, such as a high-speed camera and swept-source laser. Alternative to the above backscattering detection methods, the retroillumination microscopy by Weber and Mertz [10] demonstrates a 0.820 mm × 0.580 mm FOV.…”

“…Curved-field OCT versus full-field OCT and confocal microscopy for imaging of the SNP in the human cornea in vivo. By matching the curvature of optical sectioning with that of the cornea, CF-OCT substantially increases the FOV of the SNP layer, in comparison to the state-of-the-art TD-FF-OCT[9] and CM. Non-contact CF-OCT is free from corneal applanation artifacts, which typically complicate SNP imaging with a contact CM.…”

Unbiased corneal tissue analysis using Gabor-domain optical coherence microscopy and machine learning for automatic segmentation of corneal endothelial cells

“… 24 Auksorius et al. 25 also recently proposed a similar pipeline for volumetric images obtained with Fourier-domain full-field optical coherence tomography (OCT). The proposed pipeline used a modified U-Net neural network for the segmentation, trained with two OCT images and four SM images.…”