Effects of eye cyclotorsion and pupil centroid shift during corneal refractive surgery

Objective To evaluate the degree and direction of eye cyclotorsion and pupil centroid shiftduring corneal refractive surgery.Methods The direction and degree were measured in 140 eyes of 70 patients with myopia or myopic astigmatism.Preoperatively,an iris image of each eye was examined using the Technolas Zywave Wavefront System iris -registration feature with the patient seated.A Technolas 217Z laser was used to measure cyclotorsion on the images with the patient supine.Results One hundred and twenty-eight of 140 eyes were identified successfuly and achievement ratio was 91.4%and 54 patients were registrant bilaterally.The mean cyclotorsional misalignment was 2.59±1.91 degrees (right eye 2.67±2.00 degrees;left eye 2.51±1.98 degrees).The findings showed that there were significant differences between the two eyes.According to the absolute value of pupil centroid shift,the mean pupil centroid shift was(0.23±0. 19) mm with the X axis and(0.11±0.27) mm with the Y axis.During the 54 patients who were registrant bilaterally,the mean pupil centroid shift was(0.33±0.17) mm with the X axis and(0.11±0.27) mm with the Y axis.There were significant differences between the two eyes.Conclusion Compensation of cyclotorsion using iris registration can be helpful in decreasing misalignment of the axis of correction and in improving the overall outcome of corneal refractive surgery.