Electrical properties of lens material at microwave frequencies

Values of the complex permittivity of human and rabbit lens material in the frequency range 100--6000 MHz are reported. The data were obtained by using an on-line computer-based time-domain spectrometer. The lenses were divided into an outer (cortical) zone and an inner (nuclear) zone and the dielectric properties of each zone were measured separately for both species of lens. The results are analysed in terms of the aqueous and protein constituents, assuming a molecular model whereby the hydrated protein molecule is represented by a spherical particle embedded in an aqueous continuum. It is shown that for lens material taken from the nuclear zone the particle can be separated into protein and bound water (water of hydration). For the cortical zone the amount of water of hydration is smaller and, within the limitations of the model and uncertainties due to experimental error, cannot be distinguished from zero.