Intraocular pressure during corneal flap preparation: comparison among four femtosecond lasers in porcine eyes.

PURPOSE To compare the course of intraocular pressure (IOP) during corneal flap preparation using four different femtosecond lasers in porcine globes. METHODS Forty-eight (12 in each group) enucleated globes were successfully cannulated through the optic nerve. Intraocular pressure was measured continuously through the cannula during a normal lamellar flap creation (regular procedure) using four femtosecond lasers (IntraLase, Abbott Medical Optics; VisuMax, Carl Zeiss Meditec AG; Femtec, Technolas Perfect Vision; and Femto LDV, Ziemer Ophthalmic Systems AG). In an additional measurement (worst-case procedure), the patient interface was pressed against the globe with increasing force until the applanation maneuver was automatically aborted by those devices capable of doing so. RESULTS During the regular procedure, the maximum IOP reached was 135±16 mmHg when using the Intra-Lase, 65±20 mmHg with the VisuMax, 205±32 mmHg with the Femtec, and 184±28 mmHg with the Femto LDV. During the worst-case procedure, a maximum IOP of 260±53 mmHg was reached with the IntraLase, 105±13 mmHg with the VisuMax, and 248±51 mmHg with the Femtec. CONCLUSIONS There is considerable variation in IOP among the tested femtosecond lasers during a regular lamellar flap creation and during the worst-case procedure. The VisuMax femtosecond laser seems to cause the lowest IOP rise in both settings.