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Maximilian Franke, Timm Landes, Theo G. Seiler, Alexander Heisterkamp, Dag Heinemann, Tammo Ripken; Depth dependent measurements of the concentration of riboflavin to make the crosslinking (CXL) treatment safer. Invest. Ophthalmol. Vis. Sci. 2019;60(9):330.
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One major limitation in corneal crosslinking (CXL) for keratoconus is the required minimal thickness of 400 µm prior to UV-irradiation in order to protect the endothelium from oxidative cellular damage. In this study, we measured stromal riboflavin gradients of different imbibition solutions with various riboflavin concentrations by 2-photon fluorescence microscopy to determine UV-light availability as a function of depths.
Porcine corneas were mounted into artificial anterior chambers and divided into 3 different groups. After the establishment of stable hydration conditions each group received a 30 minutes imbibition of 15% dextran solution containing either 0.1% (group 1), 0.3% (group 2) or 0.5% riboflavin (group 3). Riboflavin concentration gradients were measured by 2-photon fluorescence microscopy. To correct the data for absorption and scattering, each cornea was saturated with the corresponding solution and measured a second time. Using the obtained riboflavin gradients, a UV-transmission as a function of depth was calculated for the 3 groups.
Intrastromal riboflavin concentration is greater when using higher concentrations during imbibition. The integral of the riboflavin concentration at a depth of 400 microns using a 0.1% imbibition is comparable to 70 microns using the 0.5% riboflavin respectively. The integral of the riboflavin concentration for 0.3% is between those of 0.1% and 0.5%.
Higher concentrated riboflavin imbibition may become an alternative for crosslinking in thin corneas. Although safety for the endothelium can be assumed with this approach, efficacy of possible new protocols need to tested biomechanically prior to a clinical introduction.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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