Comparative micromorphologic in vitro porcine study of IntraLase and Femto LDV femtosecond lasers

Abstract

To assess flap creation and stromal bed quality of 2 femtosecond refractive surgery lasers in laser in situ keratomileusis. Augenklinik am Neumarkt, Cologne, Germany. Corneal flaps were created in 115 freshly enucleated porcine eyes using the 60 kHz IntraLase FS laser (Advanced Medical Optics) and a prototype model of the Femto LDV femtosecond laser (Ziemer Ophthalmic Systems AG). The parameters that were evaluated included actual versus intended thickness by subtraction pachymetry, cutting and total suction time, quality of flap edges, and smoothness of flap beds. Confocal microscopy (Atos PLmu [Altos GmbH]) was used to objectively determine the root mean square (RMS) of the surface roughness of the stromal bed. Cutting time was 31 seconds for the 60 kHz IntraLase FS laser and 38 seconds for the Femto LDV laser. With both lasers, the standard deviation in achieved versus intended flap thickness was small (136 microm +/- 10 and 130 +/- 9 microm, respectively). Under micromorphologic examination, stromal bed quality was slightly better with the IntraLase. The RMS of bed roughness was 1.6 +/- 0.5 microm with the IntraLase and 2.0 +/- 0.4 microm with the Femto LDV. Neither laser showed significant thermal or mechanical damage in adjacent tissue layers of the stromal bed. The laser-induced bubble layer was more pronounced with the IntraLase. The laser cuts of the IntraLase FS and Femto LDV femtosecond lasers were equally smooth and of excellent quality. The standard deviation of the flap thickness was small and equal in both systems.