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M. A. Blair, C. D. Reilly; High Order Aberrations in Femtosecond Laser Flap Creation for Laser in situ Keratomileusis. Invest. Ophthalmol. Vis. Sci. 2009;50(13):551.
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This study evaluates the changes in ocular HOAs (high-order aberrations) during femtosecond laser flap creation for laser in situ keratomileusis.
17 eyes of 10 patients who underwent femtosecond laser flap creation for laser in situ keratomileusis were examined using the Oculus Pentacam. Three measurements were obtained: 1) Prior to any surgical intervention 2) After the femtosecond laser flap cut and resolution of any gas bubbles 3) After the flap was lifted and returned to its anatomic position prior to ablation. Mean RMS (root mean square) values of HOAs and each Zernike polynomial from the second to the sixth order were compared and analysis was performed to assess the changes in HOAs associated with the stages of laser flap creation and flap lifting.
Overall HOA RMS did not differ significantly throughout the laser flap creation and flap lift (p= 0.54); however, individual Zernike polynomials did reveal a significant change. A significant increase in Secondary Astigmatism (p=0.001) was noted during laser flap creation. A significant change in Spherical Aberration (p=0.04), Tertiary Astigmatism (p=0.01), and Secondary Spherical Aberration (p=0.009) was noted to occur during the flap lift and return to its anatomic position. Finally, it was noted that from pre-procedure measurements to post flap lift there was an increased incidence of Trefoil (p=0.02) and Secondary Spherical Aberration (p=0.04)
Overall HOA RMS does not change during the creation of a femtosecond laser flap or when the flap is lifted and replaced.; however, individual HOA Zernike terms do demonstrate statistically significant differences during the procedure. This is the first such study to describe these changes. The clinical significance of these findings has yet to be determined.
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