The Research And Analysis Of Pupil Centroid Shift And Cycloduction During LASIK

Objective:To study the pupil centroid shift and eye cyclotorsion characteristics of Chinese myopic patients between the wavescan wavefront examinations and surgery during LASIK.Methods:Wavescan wavefront^TM system of VISX 3.67 edition was used to take wavescan wavefront examinations and iris images for 565 eyes(285 patients) with natural pupil in dark room.Additionally,an infrared camera was mounted on the Visx Star S4-IR Excimer Laser systerm to obtain another image immediately before the laser was fired.After the surgery,these two images were compared to determine pupil center locations and cycloduction between the measurement and surgery.Results:1.Pupil center shift:Pupil center shift between the measurement and surgery occurred in all the eyes.Right eyes:112(39.6%) pupil center locations were shifted to superior-nasal quadrant;71(25.1%) pupil center locations were shifted to inferior-nasal quadrant;49 (17.3%) pupil center locations were shifted to inferior-temporal quadrant;48(17.0%) pupil center locations were shifted to superior-temporal quadrant.Left eyes:139(49.3%) pupil center locations were shifted to superior-nasal quadrant;100(35.5%) pupil center locations were shifted to inferior-nasal quadrant;19(6.7%) pupil center locations were shifted to inferior-temporal quadrant;15(5.3%) pupil center locations were shifted to superior-temporal quadrant.2.The distance of pupil centroid shift:The average pupil centroid shift of right eyes was 0.33±0.25mm.The average pupil centroid shift of left eyes was 0.34±0.27mm.The differences of the average pupil centroid shift are no statistically significant difference between the right eyes and left eyes(P＞0.05).3.The degree of eye cyclotorsion:The cycloduction between the measurement and surgery occurred in 557 eyes.The rotation dimensionality of right eyes ranges from 0.1 to 9.5 degree and the average rotation dimensionality of right eyes was 3.8±3.95 degree.The rotation dimensionality of left eyes ranges from 0 to 8.8 degree and the average rotation dimensionality of left eyes was 2.4±2.95 degree.The differences of the mean rotation dimensionality between the right eyes and left eyes are of statistically significance(P＞0.05). 4.The orientation of eye cyclotorsion:Abtorsions occurred more often than torsions in the right eyes,and there was no significant difference between abtorsions and torsions in left eyes.Conclusions:1.Pupil center shift:Pupil center shift between the measurement and surgery occurred in all eyes. many pupil center locations were shifted to its superior-nasal quadrant.2.The differences of the average pupil centroid shift have no statistically significant difference between the right eyes and left eyes(P＞0.05).3.The differences of the average rotation dimensionality between right eyes and left eyes are statistically significant(P＞0.05).4.Abtorsions occurred more often than adtorsions in the right eyes,and there was no significant difference between abtorsions and torsions in left eyes.5.Custom Vue^TM LASIK with iris registration may be useful for correcting eye cycloduction and pupil centroid shift.