Ocular cyclotorsion according to body position and flap creation before laser in situ keratomileusis

Purpose

To evaluate the degree and direction of ocular cyclotorsion according to body position and flap creation before laser in situ keratomileusis (LASIK).

Setting

Department of Ophthalmology and Visual Science, Kangnam St. Mary's Hospital, Seoul, Republic of Korea.

Methods

The rotational position 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 Visx WaveScan Wavefront System (Advanced Medical Optics) iris-registration feature with the patient seated. A Visx Star S4 laser (Advanced Medical Optics) was used to measure cyclotorsion on the images before flap creation with the patient supine. The iris image was measured again after flap creation with the patient supine. The hinge of the LASIK flap was placed on the superior side and by rotating from the right to left side.

Results

The mean cyclotorsional misalignment was 2.59 degrees ± 1.91 (SD) (right eye, 2.67 ± 2.00 degrees; left eye, 2.51 ± 1.98 degrees). Twenty eyes (13.0%) had cyclotorsion greater than 5 degrees. Seventy-six eyes (54.3%) had excyclotorsion. After flap creation, 107 eyes (76.4%) and 27 eyes (19.3%) rotated in the direction of identity and opposition, respectively. In eyes with cyclotorsion of identical direction, the mean increase was 1.27 ± 0.99 degrees and 1.19 ± 1.08 degrees in the excyclotorsion direction and incyclotorsion direction, respectively.

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 LASIK.