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Samer N. Arafat, Anita N. Shukla, Claes H. Dohlman, James Chodosh, Joseph B. Ciolino; Cross-linking Donor Corneas for the Boston Keratoprosthesis: A Method of Increasing Resistance to Collagenolytic Degradation. Invest. Ophthalmol. Vis. Sci. 2012;53(14):6072.
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To determine the optimal UVA/riboflavin cross-linking method that increases the resistance of corneas to enzymatic degradation.
The corneal epithelium of mature white New Zealand rabbit eyes were mechanically removed. Fit into Barron® artificial anterior chambers, the corneas were pre-treated with 0.1% riboflavin/20%dextran T500 every 2½ minutes for 15 minutes followed by ultraviolet A light (UVA) (= 370nm, irradiation = 3mW/cm2)for 5-minute intervals, while applying riboflavin between irradiations. The anterior cornea (A), posterior cornea (P) and the combined anterior and posterior cornea (A+P) were irradiated for the following durations: 7.5A, 7.5A+7.5P, 15A, 15A+15P, 30A, 30A+30P, 60A and 15P minutes. Gamma-irradiated corneaswere also cross-linked for 30 minutes (G+30A). The primary control was non-cross-linked corneas (no riboflavin/no UVA). Secondary controls included riboflavin only (no UVA), UVA only (no riboflavin) and Gamma-irradiated only (no UVA, no riboflavin). Corneas in each group (N≥4) were trephined into 8.5-mm buttons and incubated in 0.3% collagenase A solutions at 37°C rotating at 150 rpm. The time to total dissolution of the cornea was recorded as a measure of resistance. All groups were compared to the primary control.
Compared to primary control (4.8±0.8h), all UVA/riboflavin cross-linked groups were statistically more resistant to degradation. The dissolution times ranged from 12.1±8.1h; p<0.003 (15P) to 50.0±8.1h; p<0.0001 (15A). There were no significant differences between the primary control (4.8±0.8h) and the non-cross-linked Gamma-irradiated corneas (5.8±0.5h). Interestingly, G+30A corneas (22.3±2.0h) dissolved twice as fast as the 30A corneas (42.9±5.7h) (p<0.004) suggesting that Gamma-irradiation reduces the resistance gained by cross-linking. When comparing anterior to posterior cross-linking, 15A corneas (50.0±8.1h) lasted 4 times longer than the 15P corneas (12.1±8.1h) (p<0.003). There were varying differences in dissolution time between A and A+P cross-linked corneas.
We have identified an optimal method to increase the corneal resistance to enzymatic degradation. This technique might be used to strengthen donor corneas that are used as carriers for the Boston Keratoprostheses to decrease the incidence of keratolysis and extrusion.
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