Interlamellar cohesion after corneal cross-linking using riboflavin and ultraviolet A light

Abstract

ABSTRACT Aims Collagen crosslinking treatment of progressive keratoconus using the photosensitiser riboflavin and ultraviolet A light of 370 nm wavelength has been shown to increase significantly the tensile strength of corneal collagen by about 300%. In keratoconus, interlamellar and interfibrillar slippage have been proposed as pathogenetic mechanisms. Therefore, the aim of this study was to assess the impact of collagen crosslinking on the interlamellar cohesive force. Methods 72 post mortem porcine eyes were divided into six different treatment groups: the untreated control group, the standard crosslinking group, the hypo-osmolar crosslinking group, the stromal swelling group, the formaldehyde group and the a-amylase group. An anterior 934 mm strip of 400 mm thickness was prepared using a lamellar rotating microkeratome. For interlamellar cohesive force measurements a splitting plane was created at 50% depth. Forceedistance profiles were recorded using a microcomputer-controlled biomaterial testing machine. Results The mean interlamellar cohesive force was 0.24 N/mm in the untreated control group, 0.26 N/mm in the standard crosslinking group, 0.25 N/mm in the hypoosmolar crosslinking group, 0.23 N/mm in hydrated corneas, 0.27 N/mm in the formaldehyde group without statistically significant difference. Only the values of the a-amylase group were statistically significantly lowered by 31.5% to 0.16 N/mm. Conclusions Surprisingly, corneal crosslinking does not increase the interlamellar cohesive force. In the a-amylase group the cohesive force was mainly decreased because of the digestion of proteoglycans. Crosslinking seems to stabilise only inter-and intrafibrillar, but not interlamellar cohesion