Non-invasive evaluation of the cornea using dielectric spectroscopy

Dielectric spectroscopy is a non-invasive contact technique that permits th e in vivo measurement of the specific electrical properties of biological t issue induced by an external electrical field. Permittivity, relaxation tim e and specific conductivity as a function of corneal hydration (wet weight/ dry weight) and temperature were measured in 10 porcine corneas. Variation of tissue hydration has a minor influence on the signal, with a significant variation of the signal being detectable only for relatively dry tissue. A much greater influence was found for temperature, in particular on relaxat ion times. Dielectric spectroscopy provides us with an opportunity to detec t structural, in particular temperature-induced changes in living tissue, i n the frequency range investigated, hydration has only a small influence on the dielectric properties of the tissue.