1. 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

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

3. 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

4. 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.

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

6. Methods
Prospective, longitudinal and experimental study.

7. 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)

8. 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

9. Results Variable Pre Post P value Spherical (D) - 3.21 ± 2.77
± 2.84
0.89
Cilinder (D)
± 0.94
± 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

10. 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

11. 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

12. 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.