Variability of lamellar corneal flap thickness at different suction ring vacuum settings during keratomilieusis

Purpose. To determine if suction ring vacuum settings above the manufacturer's recommended settings significantly alter coraeal flap thickness during keratomileusis. Methods. Eight human cadaver eyes were studied. A Phoenix Keratek microkeratome was used to create the lamellar corneal flap using a standard 160 micron insert following the standard techniques described by the manufacturer. Two vacuum pressures were studied, and the eight eyes were divided equally into two groups. In the first group of four eyes, keratomileusis was performed using the manufacturer's recommended vacuum setting of 488mm Hg. The second group of four eyes had keratomileusis performed at 600 mm Hg. Cornea flap thickness was determined centrally using a Mentor Pachypen. Results. In the 488mm Hg group, corneal flap thickness remained constant at 160 microns ±10. In the 600mm Hg group, the flap thickness varied from 0 microns to 280 microns. Two flaps in the 600 micron group exhibited irregular configurations. Conclusion. Vacuum settings are important variables in determining consistent corneal flap thickness in keratomileusis. Consistent flap thickness is more predictable at the manufacturer's recommended suction of 488mm Hg.