Specific hydraulic conductivity of corneal stroma as seen by quick-freeze/deep-etch

Previously studies of the hydraulic conductivity of connective tissues have failed to show a correspondence between ultrastructure and specific hydrau lic conductivity. We used the technique of quick-freeze/deep-etch to examin e the ultrastructure of the corneal stroma and then utilized morphometric s tudies to compute the specific hydraulic conductivity of the corneal stroma . Our studies demonstrated ultrastructural elements of the extracellular ma trix of the corneal stroma that are not seen using conventional electron mi croscopic techniques. Furthermore, we found that these structures may be re sponsible for generating the high flow resistance characteristic of connect ive tissues. From analysis of micrographs corrected for depth-of-field effe cts, we used Carmen-Kozeny theory to bound a morphometrically determined sp ecific hydraulic conductivity of the corneal stroma between 0.46X10(-14) an d 10.3X10(-14) cm(2). These bounds encompass experimentally measured values in the literature of 05X10(-14) to 2X10(-14) cm(2). The largest source of uncertainty was due to the depth-of-field estimates that ranged from 15 to 51 nm; a better estimate would substantially reduce the uncertainty of thes e morphometrically determined values.