Spatial arrangement of collagen fibrils in normal and keratoconus human cornea studied by low‐frequency dielectric spectroscopy

Abstract

AbstractPurpose Spatial structure of collagen lamellae of the human cornea is thought to be an important determinant of corneal rigidity. Analysis of the low‐frequency (1–107 Hz) dielectric spectra of the normal and keratoconus human cornea in the temperature range of 140‐300 K and for different hydration states were examined.Methods For the measurements, the 100 – 200 μm specimens containing the middle layers of corneal stroma were used. The 9 specimens of healthy, control corneas from Eye Bank were obtained with second microkeratom section during Ultra Thin‐DSAEK. The 12 specimens of keratoconus corneas were manually prepared from corneas removed during penetrating keratoplasty.Results Experimental results were interpreted in terms of ionic diffusion and space charge polarization according to the Sawada’s theory. The new presentation of the dielectric spectra, i.e.: (delta eps’/delta ln f)*f, was used. The presented method and the Sawada’s expression were applied to the analysis of the changes in spatial molecular structure of collagen fibril network in human cornea.Conclusion Fitting procedure of the theoretical function to the experimental data allowed us to determine two diffusive relaxation regions with two structural distance parameters ds, describing spatial arrangement of collagen fibrils in cornea.