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Stacy L. Littlechild, Gage Brummer, Gary Conrad; Fibrinogen, Riboflavin And UVA To Immobilize The Lasik Flap In Cornea. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5193.
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Laser-Assisted In Situ Keratomileus (LASIK) is a common procedure used to correct eye conditions such as nearsightedness, farsightedness and astigmatism. One liability that results from this procedure is that the permanent flap that results from cutting into and exposing the middle layer of the cornea (the stroma), forever remains non-attached to the underlying laser-modified stroma. Such a potentially loose layer represents a medical risk. To decrease the risk of re-exposure of the stroma and immobilize this LASIK flap, a protocol using fibrinogen, riboflavin and UVA light (RF+FIB+UVA) was tested for its ability to adhere the layers of the stroma resulting from LASIK surgery.
To represent the LASIK flap, a model flap was created in the isolated corneas of the Spiny dogfish shark (Squalus acanthias) and white albino rabbits (Oryctolagus cuniculus). Then, experimental and control solutions were applied between the stromal flap and underlying stroma. Protocol controls included varying the solution applied between the stromal layers to contain either riboflavin only (RF), fibrinogen only (FIB) or both (RF+FIB). Experimental corneas received RF+FIB and long wavelength (365nm) ultraviolet light (UVA). To quantitatively measure the adhesion strength, corneas were attached to a digital force gauge with computer software to record the peak tension as the stromal flap was pulled from the underlying stroma surface at a constant rate.
The experimental RF+FIB+UVA protocol generated adhesion that reached an average peak tension of 2.09 Newtons (N) in sharks and 0.075N in rabbits whereas controls, such as RF only, reached an average peak tension of only 0.765N in sharks and 0.03N in rabbits. Similarly, the current LASIK protocol, which uses no RF, FIB or UVA to seal the LASIK flap, produced an average peak tension of only 0.395N in sharks and 0.031N in rabbits. From the data collected, the RF+FIB+UVA protocol generates an average of an 5.3-fold increase in adhesion strength over the current LASIK protocol in sharks and a 2.4-fold increase in rabbits. Further data are being collected from other controls.
These results suggest that some molecules currently in clinical trials for treating keratoconus, may also be used to immobilize the LASIK flap onto its laser-modified stroma, thus reducing risk of flap dislodgement.
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