Tensioactive-mediated Transepithelial Corneal Cross-linking – First Laboratory Report

Abstract

Purpose: The aim of this study was to investigate the possibility of delivering riboflavin into the corneal stroma for cross-linking with the aid of a tensioactive substance (benzalkonium chloride), without removing the epithelium, in order to make corneal cross-linking (CXL) a less invasive technique. Methods: Rabbit corneas were cross-linked in vivo without removal of the epithelium, using riboflavin solution 0.1% to which benzalkonium chloride solution was added. The corneas were then examined by light and electron microscopy for evidence of collagen cross-linking. Control non-treated eyes were compared with treated ones. Results: The treated corneas were stiff and yellow in colour, and on light microscope examination they showed straight compact collagen fibres in comparison with control corneas in approximately 50% of the corneal thickness. Electron microscopy revealed regular arrangement of fibres in the outer 200µm with reduced inter-fibre distances in the treated corneas, but with no noticeable differences between control and treated corneas in the inner 100µm. Conclusion: The addition of benzalkonium chloride to the riboflavin solution facilitated its entry to the corneal stroma through the epithelium, and CXL occurred without epithelium removal. KeywordsBenzalkonium chloride, collagen fibres, corneal cross-linking, epithelium, riboflavin, ultraviolet A Disclosure: The authors have no conflicts of interest to declare. Materials and MethodsThe cross-linking was carried out at the Zooprophylaxis Institute,

Safety and Efficacy of Epithelium-On Corneal Collagen Cross-Linking Using a Multifactorial Approach to Achieve Proper Stromal Riboflavin Saturation

“…Previous studies report conflicting results on the effects of epithelium-on CXL. While Pinelli and colleagues reported no significant difference in the analyzed parameters between epithelium-on and standard CXL [ 28 ], Wollensak and Iomdina found that the corneal biomechanical stiffening after epithelium-on CXL was about one-fifth compared to the epithelium-off CXL in an animal model [ 4 ]. Other clinical and laboratory studies have reported weaker or no effect of CXL using the epithelium-on method [ 22 , 23 , 25 , 29 – 31 ].…”

Corneal Collagen Cross-linking Combined With Simulation of Femtosecond Laser–Assisted Refractive Lens Extraction

“…30 There is thus inconclusive evidence in the peer-reviewed literature on the aspect of efficacy of some epithelium-on CXL variations. 3,8,26,31,32 The in situ riboflavin application naturally overcomes the first of the 2 obstacles, related to riboflavin penetration through the intact epithelium and in acting as a "blocking" agent against UV-A propagation. This is because the epithelium and Bowman layer, that the UV-A light has to transcend, are not soaked in riboflavin.…”

Transepithelial corneal crosslinking in treatment of progressive keratoconus: 12 months’ clinical results

“…The stratified corneal epithelium with tight junctions presents as a lipophilic barrier to the absorption of the hydrophilic riboflavin macromolecule. Standard riboflavin formulations were modified with addition of EDTA, benzalkonium chloride (BAC), trometamol, which loosen up the epithelial junctions, enhancing the permeability and riboflavin diffusion across the epithelium and superficial stroma 6,10. However cumulative dose of BAC in ParaCel alone may result in damage to the superficial corneal epithelial cells11 as its effect is concentration and dose dependent 12.…”

“…Standard riboflavin formulations were modified with addition of EDTA, benzalkonium chloride (BAC), trometamol, which loosen up the epithelial junctions, enhancing the permeability and riboflavin diffusion across the epithelium and superficial stroma. 6 , 10 However cumulative dose of BAC in ParaCel alone may result in damage to the superficial corneal epithelial cells 11 as its effect is concentration and dose dependent. 12 A recent two stage application of initial ParaCel containing BAC followed by BAC and dextran free vibeX Xtra combined with accelerated UVA irradiance protocols (total energy dose of 5.2j/cm 2 or 7.2 j/cm 2 ), reduced riboflavin soak time and promoted epithelial integrity, 13 maximizing patient comfort and disease stabilization.…”