To compare four different femtosecond laser devices (IntraLase FS, Zeiss VisuMAX, and Ziemer Femto LDV, and a prototype Schwind SmartTech Nanolaser) in human donor eyes with regard to their effects on IOP during femtosecond laser flap cutting. In order to get cuts parallel to the corneal surface, the cornea has to be forced into a defined shape and current femtosecond laser devices either use a flat or a curved patient interface design to achieve applanation. IOP was measured in enucleated eyeballs (n = 46) not suitable for keratoplasty by direct cannulation of the vitreous body. A second cannula was inserted to adjust IOP to a baseline pressure of 20 mm Hg. The eyeballs were lifted by custom made supporting stands to achieve an appropriate height and put under the femto-LASIK devices. The flat patient interfaces gave rise to higher IOPs (IOP max = 328.3 ± 29.8, 228.8 ± 28.4, and 201.09 ± 21.4 mm Hg), whereas the curved patient interface caused lower IOPs in response to attachment and suction (IOP max = 104.9 ± 13.4 mm Hg). Based on previous findings of visual field defects after LASIK, and as a consequence of the present study, it seems feasible to design patient interfaces in a more physiologic manner to prevent high IOPs during refractive procedures.