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Static and dynamic rotational eye tracking during LASIK treatment of myopic astigmatism with the Zyoptix laser
Irmingard M Neuhann1, Barbara A M Lege, Markus Bauer
1Tübingen University Eye Hospital, Tübingen, Germany. irmingard.neuhann@med.uni-tuebingen.de
Purpose:
To evaluate the amount of cyclotorsion and the effect of static and dynamic rotational eye tracking with the Advanced Control Eye Tracker (Bausch & Lomb) based on iris recognition in the treatment of myopic astigmatism with LASIK.
Methods:
All patients with myopic LASIK and attempted cylinder correction >0.75 diopters (D) on the Zyoptix 217z100 excimer laser platform between May 2005 and May 2007 were identified retrospectively through the existing databank. Pre- and postoperative refraction and the amount of cyclotorsion during treatment were extracted and analyzed in 828 eyes with >3-month follow-up.
Results:
Preoperative mean manifest refraction spherical equivalent (MRSE) was -4.31+/-1.84 D (range: -0.37 to -9.50 D), and mean cylinder was -1.27+/-0.87 D (range: -0.75 to -6.75 D). Mean static rotation was 3.96+/-2.96 degrees (maximum 14.8 degrees ). Median dynamic rotation was 1.32+/-1.85 degrees (maximum 24 degrees). At 3 months postoperatively, MRSE was -0.10+/-0.36 D (range: -2.25 to +1.25 D), and mean cylinder was -0.33+/-0.35 D (range: -2.00 to 0 D). Predictability was 90.2% within +/-0.50 D and 98.2% within +/-1.00 D (MRSE), and 82.5% within +/-0.50 D and 96.9% within +/-1.00 D (cylinder). The efficacy ratio was 0.99. Safety was 99.4% (5 dry eyes), reaching 100% at 12 months. Stability from 3 to 12 months (n=275) was 98.2% for sphere, 95.3% for cylinder, and 96.0% for MRSE.
Conclusions:
Our study demonstrates that significant cyclotorsion occurs before and during treatment. By using the dynamic rotational eye tracker presented, the efficacy of cylinder correction can be improved compared to those studies not performing cyclotorsional correction.