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Viacheslav Mazlin, Peng XIAO, Kate Grieve, Jose A. Sahel, Mathias Fink, Claude Boccara; A novel non-contact instrument for en face cellular resolution imaging of in vivo human cornea based on full-field OCT. Invest. Ophthalmol. Vis. Sci. 2018;59(9):3437.
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Up to now the only clinical technique capable of providing en face images of the in vivo cornea with cellular-level resolution was confocal microcopy; however the requirement of contact with the eye and the small field-of-view (300 µm x 300 µm) limit its applications. We tested a new non-contact, 1.3 mm x 1.3 mm field-of-view, cellular-level resolution device, based on full-field OCT (FFOCT), to image the cornea in vivo.
Corneal images were obtained from three healthy subjects using the FFOCT instrument. No contact with the eye was required. Stacks of 40 en face images were acquired at a speed of 275 en face frames per second, with each frame being captured in 3.4 milliseconds. Unsuccessful images, captured during fast axial eye movements, were excluded from the stack, and an image registration algorithm was applied to the rest of the stack to compensate for the slow lateral eye movements. Registered images were then averaged to obtain high signal-to-noise final frames. Confocal microscopy (HRT II, Heidelberg) data were obtained on the same subjects for comparison.
In vivo corneal epithelium, Bowman’s layer, sub-basal nerve plexus (SNP), stromal keratocytes, stromal nerves, Descemet’s membrane (DM) and endothelial cells with nuclei were visualized using FFOCT. Nuclei of the anterior, middle and posterior stromal keratocytes had diameters of 13 ± 4 µm, 20 ± 5 µm and 19 ± 7 µm, respectively. Keratocyte nuclei had an oval shape, which became more oblong with depth. Thicknesses of the SNP and stromal nerves were measured to be 4 ± 1 µm and 8 ± 1 µm, respectively. Endothelial cells had diameters of 20 ± 1 µm with nuclei of 3.5 ± 1 µm. Cells were hexagonal in shape with round nuclei. These results are in agreement with the confocal microscopy data from the same subjects.
FFOCT is a new eye imaging modality, allowing non-contact visualization of millimeter-field regions of in vivo human cornea with cellular resolution. Dimensions and shapes of the structures observed in FFOCT are in agreement with those seen with clinical confocal microscopy. The non-contact, wide field acquisition presents advantages in terms of patient comfort and clinical value in comparison to confocal microscopy, and the superior resolution is an advantage compared to conventional OCT.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
In vivo human cornea images obtained with FFOCT, compared with clinical confocal microscopy.
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