Evaluation of the Ocular Cyclotorsion During Laser in Situ Keratomileusis

ABSTRACT

PURPOSE: To evaluate the presence, degree and direction of ocular cyclotorsion in eyes undergoing laser in situ keratomileusis (LASIK). METHODS: We measured the presence, degree and torsional direction of 161 eyes of 88 patients who underwent LASIK for myopic and hyperopic astigmatism with LADARVision 4000 excimer laser (Alcon Summit Autonomous). Preoperatively, each eye was marked at the 3, 9-o'clock conjunctival area with marking pen under the slit lamp observation with a horizontal beam while the patient was seated upright. After lifting of corneal flap and acquiring of LADARVision4000 auto-tracking system, the presence and torsional direction was confirmed on the computer monitor and the rotational deviation degree was measured from horizontal reference line by software program built in laser computer system before the laser exposure. RESULTS: There was a cyclotorsional deviation in 144 eyes (89%). The counter-clockwise rotation was shown in 99 eyes (69%) and clockwise rotation in 45 eyes (31%). Mean ocular torsional misalignment was 3.8 +/- 2.9 degrees (right eye; 4.7 +/- 2.9 degrees, left eye; 3.5 +/- 2.4 degrees). 85 eyes (53%) had a torsional deviation less than 4 degrees and 5 eyes (3%) had a deviation greater than 10 degrees. CONCLUSIONS: A misalignment of astigmatism axis caused by ocular cyclotorsion was known as a reason of astigmatism undercorrection during LASIK. Thus, preoperative marking on conjunctiva and cyclotorsional axis alignment before laser treatment may reduce the incomplete astigmatism correction in LASIK.