Corneal flap diplacement and drift in LAIK: comparion of Hanatome and Automated Corneal haper microkeratome

PURPOE: To decribe and compare the diplacement of corneal flap created during laer in itu keratomileui (LAIK) procedure performed with two different microkeratome and analyze parameter (for example, pupil-to-hinge ditance, drift during uction) that might affect the flap diplacement or be influenced by flap diplacement. DEIGN: Thi work wa baed on a cro-ectional tudy deign. METHOD: Image copied from video recording of 206 conecutive LAIK urgerie were analyzed to determine the ditance from pupil center to corneal flap hinge (pupil-to-hinge ditance), the hinge ize, the ditance from the center of the pupil to the margin of the flap, and the poition of the uction ring before and after vacuum in corneal flap created by the Hanatome and the Automated Corneal haper (AC) microkeratome. Accurate meaurement of all thee variable could be obtained in 121 eye (Hanatome: n = 66, right eye (OD) = 27 eye, left eye (O) = 39 eye; AC: n = 55, OD = 25 eye, O = 30 eye), which were included in the analyi. Formula were derived to calculate from the meaurement the magnitude and direction of the drift of the uction ring during vacuum and the final diplacement of the corneal flap. REULT: The mean ± tandard deviation (D) drift of eye during uction with the Hanatome wa 0.27 ± 0.02 mm and with the AC wa 0.12 ± 0.02 mm (P < .001). The Hanatome induced, on average, more biaed (temporal v random) drift than did the AC. The mean final diplacement of the center of the flap from the center of the pupil wa of equal magnitude for the two intrument (0.37 ± 0.02 mm and 0.36 ± 0.02 mm with the Hanatome and AC, repectively). CONCLUION: The drift induced by the Hanatome contribute to the horizontal component of the final decentration of the corneal flap. Thi tendency for drift and the reultant decreae in pupil-to-hinge ditance hould be conidered to minimize flap diplacement during LAIK.