Differential permeability rate and percent clearing of glucose in different regions in rabbit sclera

Imaging of biological tissues with optical coherence tomography (OCT) poses a great interest for its capability to noninvasively outline subsurface microstructures within tissues. However, a major limitation for many optical imaging techniques is inadequate depth penetration of light in turbid media, which is bounded to just a few millimeters. There have been several attempts to improve light penetration depth in biological tissues, including application of different tissue optical clearing methods. In this study, an aqueous solution of glucose (40%) is added to rabbit sclera in vitro, where depth-resolved permeability coefficients and optical clearing are calculated with OCT. The permeability rate in regions in the upper 80- to 100-microm region is found to be different from that of regions in the deeper 100-microm region: (6.01+/-0.37)x10(-6) cmsec and (2.84+/-0.68)x10(-5) cmsec, respectively. A difference in percent clearing is also noted. Optical clearing of the upper region is about 10% and increased to 17 to 22% in the one beneath. These results demonstrate the capability of OCT-based methods to not only measure the diffusion rate and optical clearing of a tissue, but also its ability of functional differentiation between layers of epithelial tissues.