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

Objective To measure the eye cyclotorsion and pupil centroid shift of Chinese myopic patients during corneal refractive surgery.Methods One hundred and seventy-two eyes of 86 consecutive myopic patients who had bilateral CustomVueTM corneal refractive surgery were involved in the study.Wavefront measurement and iris registration were performed in the upright position with Wavescan aberrometer,and another iris registration was performed in the supine position during the operation with VISX Star S4 IR.Results One hundred and forty-seven of 172 eyes were registrant successfully and 63 patients were registrant bilaterally.The rotations were divided into four categories:(1) Excyclotorsion:counterclockwise rotation in the right eye and clockwise in the left eye:60 eyes;(2)Incyclotorsion:clockwise rotation in the right eye and counterclockwise in the left eye:4 eyes;(3) Counterclockwise rotation in both eyes:44 eyes;(4)Clockwise rotation in both eyes:18 eyes.Among the 147 eyes registrant,38 eyes had a rotation ≤1°,29 eyes of 1.1°~2.0°,22 eyes of 2.1°~3.0°,21 eyes of 3.1°~4.0°,17 eyes of 4.1°~5.0°,13 eyes of 5.1°~6.0°,7 eyes above 6.1°.The mean absolute value of rotation angle was 2.6°±1.9°,ranging from 0.1° to 8.6°.The mean pupil centroid shift was (0.348±0.144) mm (0.064~0.539 mm),with (0.27±0.16) mm (0~0.50 mm) in the X axis and (0.17±0.12) mm (0~0.48 mm) in the Y axis.Conclusion Eyes can have a cyclotorsion and pupil centroid shift when going from the upright to the supine position.CustomVueTM with iris registration may be a useful tool for the measurement of eye cyclotorsion and pupil centroid shift.