Purchase this article with an account.
Stacy L. Littlechild, Gage A. Brummer, Yuntao Zhang, Gary W. Conrad; Fibrinogen, Riboflavin and UVA to Immobilize the LASIK Flap in Cornea. Invest. Ophthalmol. Vis. Sci. 2012;53(14):1479.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
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 containing combinations of riboflavin (RF) and fibrinogen (FIB) were applied between the stromal flap and the underlying stroma. Long wavelength (365nm) ultraviolet light (UVA) was applied to the experimental corneal sets. 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. Surface Plasmon Resonance (SPR) and western blotting techniques were used to characterize the mechanism(s) of adhesion between components of the glue and corneal extracelluar matrix (ECM) molecules.
The experimental RF+FIB+UVA protocol generated adhesion that reached an average peak tension of 2.47 Newtons (N) in sharks and 1.00N in rabbits whereas controls modeling the current LASIK protocol, which uses no RF, FIB or UVA to seal the LASIK flap, produced an average peak tension of only 0.55N in sharks and 0.20N in rabbits. From the data collected, the RF+FIB+UVA protocol generates an average of a 4.5-fold increase in adhesion strength over the current LASIK protocol in sharks and a 5-fold increase in rabbits. Additionally, western blot and SPR data demonstrated two mechanisms of adhesion were at play: The first being a covalent interaction between Collagen Type I in the corneal stroma and FIB in the glue of corneas that received RF+FIB+UVA, and the second being a noncovalent interaction between dermatan sulfate, the glycosaminoglycan (GAG) chain attached to core protein decorin, and FIB.
These results suggest that adhesion created by covalent cross-links coupled with adhesion generated by noncovalent interactions between corneal ECM molecules and FIB in the glue may be used to immobilize the LASIK flap onto its laser-modified stroma, thus reducing risk of flap dislodgement.
This PDF is available to Subscribers Only