Corneal Endothelial Changes 5 Years after LASIK: Femtosecond Laser versus Mechanical Microkeratome

Abstract

Purpose: : To determine if flap creation by a femtosecond laser is associated with corneal endothelial changes compared to flap creation by a mechanical microkeratome at 5 years after LASIK.

Methods: : In a randomized, paired-eye study, 21 patients underwent LASIK for myopia or myopic astigmatism. Eyes were randomized by ocular dominance to LASIK with the flap created by a femtosecond laser (15 kHz IntraLase FS, IntraLase) in one eye and to LASIK with the flap created by a mechanical microkeratome (Hansatome, Bausch & Lomb) in the fellow eye. Central endothelial images were recorded by confocal microscopy (ConfoScan 4, Nidek) before and at 3 and 5 years after LASIK and were analyzed by using a centers method (KSS-400, Konan). Endothelial cell density (ECD), the coefficient of variation of cell area (CV, standard deviation/mean), and the percentage of hexagonal cells (HEX) were compared between treatments at each examination by using paired t-tests with Bonferroni correction for 3 comparisons.

Results: : ECD did not differ between fellow eyes before LASIK (femtosecond laser, 2,758 ± 406 cells/mm²; mechanical microkeratome, 2,773 ± 399 cells/mm²; n=21, p=0.99) or between treatments at 3 years (femtosecond laser, 2,760 ± 383 cells/mm²; mechanical microkeratome, 2,796 ± 398 cells/mm²; n=19, p=0.99) and 5 years (femtosecond laser, 2,829 ± 317 cells/mm²; mechanical microkeratome, 2,853 ± 355 cells/mm²; n=17, p=0.99) after LASIK. The minimum detectable differences in ECD at 3 and 5 years were 129 and 120 cells/mm² respectively (α=0.05/3, β=0.20, paired analyses). CV did not differ between treatments before LASIK (femtosecond laser, 0.32 ± 0.06; mechanical microkeratome, 0.32 ± 0.05; p=0.99) and remained stable through 5 years (femtosecond laser, 0.31 ± 0.04; mechanical microkeratome, 0.32 ± 0.03; p=0.99). HEX did not differ between treatments before LASIK (femtosecond laser, 59 ± 8 %; mechanical microkeratome, 59 ± 6 %; p=0.99) and remained stable through 5 years (femtosecond laser, 57 ± 7 %; mechanical microkeratome, 58% ± 6 %; p=0.99).

Conclusions: : The energy delivered to the cornea during femtosecond laser flap creation does not affect the corneal endothelium at 5 years after LASIK when compared to flap creation with a mechanical microkeratome. Corneas that have received either method of flap creation could be accepted as donor tissue for endothelial keratoplasty.

Clinical Trial: : http://www.clinicaltrials.gov NCT00350246

Keywords: refractive surgery: LASIK • cornea: endothelium • cornea: clinical science