Ultrastructure of collagen fibrils, proteoglycans and lamellae of the human cornea treated with Iontophoresis ‐ UVA cross‐linking and hypotonic riboflavin solution

Abstract

AbstractPurposeTo investigate the effect of iontophoresis‐UVA cross‐linking with hypotonic riboflavin solution on the ultrastructural changes in the lamellae, collagen fibrils (CF) and proteoglycans (PGs) in the central and peripheral stroma of the human corneal buttons.MethodsIontophoresis method was used for the trans‐epithelial application of hypotonic riboflavin in ex vivo corneal culture for 5 minutes. The corneas were irradiated using three methods; Group 1 (G1): an UV‐A irradiance of 3 mW/cm2 for 30 minutes; Group 2 (G2): an UV‐A irradiance of 10 mW/cm2 for 9 minutes; Group 3 (G3): without UV‐A irradiation. Three untreated corneas were used as a control group (G0). After CXL procedure, the corneas were processed for electron microscopy. CF diameter and PGs in each sample were analyzed using iTEM program.ResultsThe keratocyte organelles and stromal architecture in the peripheral cornea were better preserved than in the central cornea. The mean CF diameter in the peripheral cornea of the ‘G1 and G2’ was significantly higher compared to those in the central cornea. In G3, the central corneal CF diameter was significantly larger than the peripheral corneal CF diameter. There were also differences in the PGs area size between the central and peripheral cornea in all groups.ConclusionsRiboflavin + UVA application at 3mW2 /cm for 30minutes and 10mW2/cm for 9 minutes is a suitable method of CXL; however, the 10mW2/cm for 9 minutes combination seems to present stronger phototoxic effect and better prognosis for corneal healing. CXL treatment was more effective at the periphery than center.AcknowledgmentsThis research project was funded by National Plan for Science and Technology Program (Grant Number 15MED4229‐02), King Saud University.