Abstract
Purpose:
To determinate the variability of thickness and diameter of corneal flap programmed versus obtained with femtosecond laser.
Methods:
The study design was prospective, transversal, observational and descriptive. All patients consulting for refractive surgery Laser Assisted in Situ Keratomileusis (LASIK), in which the corneal flap was created using the femtosecond laser, were selected. The thickness and diameter of corneal flap were programed in Visumax 500Hz femtosecond laser. After three months, a single observer measured the thickness of the corneal flap with optical coherence tomography of anterior segment (VISANTE OCT), taking two images along the axis from 0 to 180 degrees and making three measurements of the thickness. The diameter of the corneal flap was measured sing a caliper on the axis from 0 to 180 degrees. The data analysis regarding mean values, ranges and standard deviations were calculated with SPSS. Method comparison and evaluation were made with Bland - Altman Medcal program. We considered clinically significant a variation up to 10 microns in the programmed flap versus the obtained.
Results:
A total of 80 eyes from 40 patients were comprised. The mean age of patients included were 23.7 years, (range 20-42 years, SD 4.88). The programmed flap with Visumax 500Hz femtosecond laser was 120 microns and the diameter of corneal flap was 7.94 mm. The obtained flap had a mean thickness of 116.93 micron (range 100-128 microns, SD 4.86). The obtained corneal flap had a mean diameter of 8.01 mm (7.0 - 8.2 mm, SD 0.53).
Conclusions:
When creating a corneal flap, the femtosecond laser is predictable within clinically acceptable ranges. Comparing programmed flap versus obtained, the mean variability of thickness was in the order of 3 microns and the diameter 0.08 mm.
Keywords: 683 refractive surgery: LASIK •
479 cornea: clinical science •
578 laser