The Effect of Collagen Crosslinking Using Riboflavin/UVA on the Molecular and Fibrillar Architecture of the Corneal Stroma

Abstract

Purpose: : To measure the changes in collagen interfibrillar spacing and intermolecular spacing in porcine corneas immediately following crosslinking with riboflavin/UVA.

Methods: : 42 enucleated porcine eyes were treated using riboflavin/UVA crosslinking following the methods described by Wollensak et al. (Am J Ophthalmol. 2003;135:620-7). After crosslinking, the corneas with a small scleral rim attached, were dissected and examined at the Daresbury synchrotron radiation source. Both small angle and wide angle x-ray scattering studies were performed to measure the central average interfibrillar spacing and the average intermolecular spacing respectively.

Results: : There was a reduction in the interfibrillar spacing from 65.9±1.4nm to 60.1±1.8nm after riboflavin/UVA treatment. The intermolecular spacing, however, increased from 1.63± 0.00nm to 1.78 ±0.08nm.

Conclusions: : Comparison of the results with those from groups where either riboflavin or UVA treatment was omitted, allowed us to conclude that the reduction in the interfibrillar spacing is due to riboflavin treatment, probably a dehydration effect of the dextran used in the vehicle. The increase in the intermolecular spacing was due to crosslinking, as it only occurred when both riboflavin and UVA were used. Previous studies have revealed that crosslinking collagen fibrils (by natural ageing or by glycation) increases the spacing between the molecules. The present results confirm that the majority of the collagen molecules in the stroma are crosslinked by this treatment.

Keywords: cornea: stroma and keratocytes • cornea: basic science • keratoconus