Intraoperative Optical Coherence Tomography Using the RESCAN 700: Preliminary Results in Collagen Crosslinking

Purpose. To compare the penetration of riboflavin using a microscope-integrated real time spectral domain optical coherence tomography (ZEISS OPMI LUMERA 700 and ZEISS RESCAN 700) in keratoconus patients undergoing accelerated collagen crosslinking (ACXL) between epithelium on (epi-on) and epithelium off (epi-off). Methods. Intraoperative images were obtained during each of the procedures. Seven keratoconus patients underwent epi-on ACXL and four underwent epi-off ACXL. A software tool was developed using Microsoft. NET and Open Computer Vision (OpenCV) libraries for image analysis. Pre-and postprocedure images were analyzed for changes in the corneal hyperreflectance pattern as a measure of the depth of riboflavin penetration. Results. The mean corneal hyperreflectance in the epi-on group was 12.97 +/- 1.49 gray scale units (GSU) before instillation of riboflavin and 14.46 +/- 2.09 GSU after AXCL (P = 0.019) while in the epi-off group it was 11.43 +/- 2.68 GSU and 16.98 +/- 8.49GSU, respectively (P = 0.002). The average depth of the band of hyperreflectance in the epi-on group was 149.39 +/- 15.63 microns and in the epi-off group it was 191.04 +/- 32.18 microns. Conclusion. This novel in vivo, real time imaging study demonstrates riboflavin penetration during epi-on and epi-off ACXL