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Emilio Almeida Torres Netto, Sabine Kling, Nikki L Hafezi, James Bradley Randleman, Farhad Hafezi; Oxygen diffusion limits the biomechanical effectiveness of iontophoresis-assisted transepithelial corneal cross-linking. Invest. Ophthalmol. Vis. Sci. 2018;59(9):1385.
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© ARVO (1962-2015); The Authors (2016-present)
Transepithelial CXL protocols have been proposed to leave the corneal epithelium intact, shortening the postop healing period and decreasing the risk for infection. However, when compared with standard epi-off CXL, clinical results have been rather disappointing. The purpose of this study is to evaluate the impact of varying treatment time on the efficacy of Iontophoresis-assisted transepithelial CXL (I-CXL) in ex vivo porcine corneas.
One hundred twelve porcine corneas with intact epithelium were divided into 7 groups and analyzed. Groups 1, 2 and 3 received conventional epi-off CXL (C-CXL) with hypoosmolaric 0.1% riboflavin and 30 minutes of UV-A irradiation at 3 mW/cm2, 10 minutes at 9 mW/cm2, or were not irradiated (controls). Groups 4, 5, 6 and 7 received iontophoresis-assisted transepithelial cross-linking (I-CXL) for either 60 minutes at 1.5 mW/cm2, 30 minutes at 3 mW/cm2, 10 minutes at 9 mW/cm2, or were not irradiated (controls). Young's modulus and stress after relaxation of 5-mm wide corneal strips were analyzed.
I-CXL with a de-accelerated prolonged irradiation of 1.5 mW/cm2 for 60 minutes resulted in an increased biomechanical stiffening when compared to the other I-CXL protocols. Nevertheless, this improved stiffening effect in I-CXL still remained inferior to any of the epi-off C-CXL treated groups. In the C-CXL groups, differences were found between controls and 3mW/cm2 for 30 minutes and between controls and 9mW/cm2 for 10 minutes.
The biomechanical effect of I-CXL increased significantly when using a low irradiance/long irradiation setting. Oxygen diffusion thus may indeed represent a limiting factor even when riboflavin penetration is improved via iontophoresis. Still less effective than C-CXL, this modification may help establish transepithelial CXL as a treatment option in selected cases.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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