To quantify the cyclorotation occurring between wavefront measurement and laser refractive surgery.
LaserVue Eye Center Ophthalmic Clinic, Santa Rosa, California, USA.
The pupil camera of the Visx WaveScan® wavefront device was used to obtain images of 51 eyes (26 patients) from 5 to 20 minutes before refractive laser surgery. Additionally, an infrared camera was mounted on the Visx Star S3 ActiveTrak® excimer laser system to obtain another image immediately before the laser was fired. After surgery, the 2 sets of images were compared to determine the amount of cyclotorsion between the measurement and surgery.
Cyclorotation of individual eyes was as high as 9.5 degrees. The mean was approximately 2.0 degrees for each eye. Binocular excyclotorsion was the predominant trend, affecting 19 of 24 patients.
A low to moderate amount of cyclotorsion was observed in the transition from seated to supine position. Comparison of eye position at the time of measurement to eye position at the time of surgery can be used to adjust the laser ablation algorithm to compensate for this rotational displacement.