Detection of static cyclotorsion and compensation for dynamic cyclotorsion in laser in situ keratomileusis.

PURPOSE To evaluate the degree of static and dynamic cyclotorsion using a rotational eye tracker in laser in situ keratomileusis (LASIK) to correct myopic astigmatism. SETTING Rothschild Foundation, Paris, France. DESIGN Cohort study. METHODS Laser in situ keratomileusis with active iris registration using a Zyoptix 100 Hz excimer laser with Advanced Control Eyetracking was performed in eyes with myopic astigmatism. In all cases, iris registration was used to evaluate the degree of static cyclotorsion preoperatively and the degree of dynamic cyclotorsion and intraoperatively. The direction, mean values, and ranges of static and dynamic cyclotorsion were recorded. The amplitude of intraoperative cyclotorsion was reported. RESULTS The study included 74 consecutive eyes (38 patients). The direction of cyclotorsion was not statistically significant. The mean static cyclotorsion was 3.08 degrees ± 2.68 (SD) (range -7.0 to 14.0 degrees) and the mean dynamic cyclotorsion, 3.39 ± 2.94 degrees (range -10.3 to 13.5 degrees). During photoablation, the mean amplitude of cyclotorsion was 2.69 ± 1.63 degrees (range 0.0 to 9.2 degrees). The magnitude of dynamic cyclotorsion was less than 5 degrees in 66% of eyes, 5 degrees or more in 34% of eyes, and 10 degrees or more in 4% of eyes. CONCLUSIONS Static and dynamic cyclotorsion was detected with a dynamic eye tracker in eyes having LASIK. Rotational movements were mainly static but had significant amplitude during photoablation.