Epithelial and corneal thickness measurements by in vivo confocal microscopy through focusing (CMTF)

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Abstract
Purpose. To study the feasibility of measuring total corneal thickness, as well as the thickness of the epithelium and Bowman's layer, using a novel in vivo confocal microscopy through-focusing (CMTF) methodology. Methods. The central cornea was scanned from the epithelium to endothelium at an average focal plane speed of 32 µm/sec for rabbits, and 64 µm/sec for humans. Scans were initially video-recorded and later digitized. From digital images, CMTF intensity curves were generated by calculating the average pixel intensity in the central 180 × 180 pixel region (285 µm × 285 µm) of each image in the scan, and plotting as a function of z-depth. Peaks in this intensity profile were then empirically correlated to unique corneal layers using a program which interactively displayed images corresponding to the mouse cursor position along the intensity profile curve. Sub-layer thickness values were then calculated from the z-axis positions of the relevant peaks in the intensity curve. Ten normal rabbits and sev...