Eye movement during laser in situ keratomileusis

Purpose: To measure eye motion in patients having laser in situ keratomileu sis (LASIK) using a video technique and determine centration and variance o f the eye position during surgery. Setting: Laser refractive surgery center. Methods: The procedure was videotaped in 5 consecutive eyes having LASIK pe rformed by a single surgeon with the VISX Star S2 excimer laser. Following surgery, video images of the eyes were digitized and stored in a computer f or processing. Digitized images were obtained at a rate of 25 images per se cond during the laser procedure. The pupil margin and a visual landmark, su ch as a scleral blood vessel, were identified in the initial image of each eye. Custom software was used to track the location of the landmark and the pupil center in subsequent images. Results: Three of the 5 eyes were well centered on average, The remaining 2 eyes were decentered inferiorly by approximately 0.25 mm. The standard dev iation in all eyes was approximately 0.10 mm. Conclusions: With these techniques, the position of the entrance pupil cent er relative to the excimer laser axis could ise determined. Although the sy stem is not fast enough to be used during surgery, it does allow quantifica tion of centration and intraoperative motion after surgery. J Cataract Refr act Surg 2000; 26:345-351 (C) 2000 ASCRS and ESCRS.