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K.–M.A. Tuan, C. Campbell, G. Tuan, D.A. Chernyak; Corneal Tissue Change After Wavefront–Guided LASIK Procedure . Invest. Ophthalmol. Vis. Sci. 2004;45(13):217.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose:To acquire insight regarding the course of corneal healing by analyzing changes in corneal optical characteristics over time. Methods:Subjects had all had wavefront–derived LASIK and had all been myopic prior to their surgeries. Corneal surface elevation information was taken from Humphrey topography images. A Cartesian oval reference surface (this surface would not induce aberrations) was subtracted from the central 5.5 mm of thec orneal surface. The residual was decomposed Zernike polynomials through the 6th order to yield coefficients characterizing the induced wavefront error. Zernike polynomial coefficients were compared at 1 month, 3 months, 6 months, 9 months, and 12 months. Average changes in each Zernike polynomial coeffiecient were calculated at each follow up. Results: Zernike polynomial coefficients changed only slightly up to the 6–month exam. Of those changes, the largest occurred in defocus (Z (2_0) between the 1–month and 3–month exams. Although manifest refractions were stable, the 9–month and 12–month exams showed changes in coma and trefoil. There were also shifts toward less defocus, more astigmatism, and less spherical aberration. The cohort was divided by spectacle and contact lens use to determine if Zernike terms changed differently on that basis. There were no statistically significant differences in changes in most of the terms with the exceptions of spherical aberrations (Z(4_0) and Z(6_0)). These differences appeared at the 1M follow up, at which point the Spectacle group had more positive spherical aberration, and the Contact Lens group was close to zero spherical aberration. However, spherical aberration in the Spectacle group decreased over time, eventually resolving at a negative average spherical aberration, whereas the zero spherical aberration of the Contact Lens group was stable over the 12 months. Conclusions:Little change was observed in the corneal surfaces of post–LASIK myopia patients between 1 and 6 months. However, continuous progression of higher order aberrations was observed in some subjects. While there was a noticeable shift to negative spherical aberration in the Spectacle group over the 12 months, spherical aberration remained stable in the Contact Lens group over the same period.
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