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Luigina Sorbara, Olivera Kralj, Bingyao Tan, Ben MacLellan, Kirsten Carter, Eric Mason, Lacey Haines, Denise Hileeto, Kostadinka K Bizheva; In-vivo Imaging of the Cellular Structure of Keratoconic Human Cornea with Sub-micrometer Axial Resolution OCT. Invest. Ophthalmol. Vis. Sci. 2017;58(8):5442.
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© ARVO (1962-2015); The Authors (2016-present)
To visualize in-vivo and characterize morphometric changes in the keratoconic (KC) cornea at a cellular level with a sub-micrometer axial resolution OCT system.
We have developed a sub-micrometer axial resolution, fibre-optic SD-OCT for in-vivo, non-contact imaging of the human cornea. The OCT system operates in the 800 nm spectral region and provides ~ 0.95 µm axial and ~2 µm lateral resolution in corneal tissue, sufficient for visualization of individual cells in the corneal epithelium, collagen fibrils and keratocytes in the corneal stroma. 20 KC subjects with different stages of KC progression and healthy, age matched subjects have been imaged. The OCT images are acquired from an area of 1 mm x 1mm region in the cornea located ~ 1 mm inferiorly relative to the corneal apex. The images are analyzed with our custom Matlab-based image processing algorithms, to measure spatially dependent thickness of the corneal epithelium and Bowman’s membrane (BM) and determine the size of abnormal cell growth in the epithelium and regions of scarring in the stroma. OCT KC images were compared with histology.
OCT imaging of subjects with early stages of KC revealed mostly spatially uniform thinning of the epithelium and occasional presence of clusters of abnormal cells located at the epithelial basal cell layer. Small breaks in the BM and increased scatter from the anterior stroma were also observed with no significant morphological changes to the rest of the stroma and posterior cornea. In contrast, the OCT imaging of subjects with advanced KC demonstrated spatially dependent variation of the epithelial thickness, partial or complete disintegration of the Bowman’s membrane, extensive scarring of the stroma and overall decreased corneal thickness. There was marked variation in the central epithelial thickness ranging from 3 cellular layers (~ 20 µm) to nearly 2x that of healthy corneal epithelium.
Sub-micrometer resolution OCT is capable of visualizing the cellular structure of the healthy and KC cornea in-vivo and without contacting the corneal surface. High resolution OCT corneal imaging allows more precise morphometric analysis of the KC cornea which would provide valuable diagnostic and prognostic insights for clinicians in terms of determining the optimal course of treatment of KC.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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