Asociación Para Evitar La Ceguera En México Hospital Dr. Luis Sánchez Bulnes Cornea And Refractive Surgery Departament Changes in Ocular Aberrations and Manifest Refraction Induced by the Creation of a Flap with a Femtosecond Laser Manuel Alejandro Garza León MD Gabriela Ortíz Nieva MD Patricia Culebro MD Jorge Ozorno Zárate MD Ramón Naranjo Tackman MD

The authors has no financial interest in any products discussed in this presentation

Introduction Some studies report that the LASIK flap may induce high order aberrations (HOAs) The characteristics of the ideal corneal flap are Reproducible in both size and thickness Smooth stromal surface, A stable hinge, Uniform central and peripherical thickness so it helps with the correct alignment, Don´t introduce aberrations nor changes in the refraction

Introduction The IntraLase femtosecond laser software creates a circular cleavage plane starting at 1 side of the cornea and progressing across the cornea using a raster pattern. Flaps created with femtosecond laser have showed a great reproducibility in size and thickness, less astigmatic change and better UCVA and manifest refractive outcomes.

Purpose To know the effect of the corneal flap creation with the femtosecond laser in optical wavefront aberrations and subjective manifest refraction

Methods Prospective, longitudinal and experimental study.

Methods The changes produced by the flap creation were studied under the following variables: Spherical and cylindrical manifest refraction Axis of astigmatism Match Total root mean square (RMS) High order RMS (coma, spherical aberration, trefoil, 4th order vertical and horizontal astimatism, as well as the quadrafoil)

Results 20 eyes of 10 patients, were evaluated, average age of 20 years old. 7 were female. None of the evaluated parameters had a statistically significant difference (p < 0.05) the mean sphere and cylinder went up Change in the axis of astigmatism of 17.4º The Match was slightly diminished The total and the high order RMS went up. Other studied aberrations didn't suffer statistically significant changes

Results Variable Pre Post P value Spherical (D) - 3.21 ± 2.77 - 3.38 ± 2.84 0.89 Cilinder (D) - 2.27 ± 0.94 - 2.44 ± 0.94 0.69 Axis (g) 60.2 ± 77 42.8 ± 65.9 0.59 Match (%) 91.60 ± 5.54 90.30 ± 7.21 0.66 RMS (µm) 7.52 ± 3.30 7.75 ± 3.34 0.88 RMS HOAs (µm) 0.49 ± 0.11 0.54 ± 0.07 0.26

Results Aberration (µm) Pre Post P value Coma 0.243± 0.11 0.265± 0.12 0.69 Spherical Aberration 0.207± 0.13 0.222± 0.16 0.82 Trefoil -0.164±0.19 -0.232±0.17 0.43 Quadrafoil 0.000±0.04 0.005±0.05 0.83

Discussion This prospective study results confirms previous reports of better manifest astigmatism outcomes with the IntraLase laser. Previous reports demostrated a significant increase in HOAs in Hansatome flaps so the femtosecond laser may be the best microkeratome choice for wavefront-guided LASIK and larger optical zone treatment Kezirian GM, Stonecipher KG. J Cataract Refract Surg 2004; 30:804–811 Tran DB, Sarayba, MA, Bor, Z, et al. J Cataract Refract Surg 2005; 31:97–105

Conclusions Creation of the corneal flap with superior hinge with femtoseconds laser has no significative effect in the refractive state and the wavefront aberrations of the eye.