Improvement in photorefractive corneal laser surgery results using an active eye-tracking system

Abstract

Purpose: To study the advantage of modern eye-tracking systems for photorefractive surgery. Setting: Department of Ophthalmology, University of Zurich, Zurich, Switzerland. Methods: Photorefractive surgery (photorefractive keratectomy and laser in situ keratomileusis) for myopia and myopic astigmatism was performed in 40 eyes with a commercially available medical excimer laser system. The eyes were selected retrospectively from a larger group of patients treated at 1 clinic. In 20 eyes, the ablation was centered on the entrance pupil using the active, video-based, eye-tracking system (sampling frequency 50 Hz) of the laser. During laser treatment in the nontracker group (20 eyes), the active eye-tracking system was switched off and centration was done manually by the surgeon. Preoperatively and 1 and 3 months after surgery, the patients had a standard ophthalmic examination as well as wavefront analysis by means of a custom-designed wavefront analyzer. Results: After surgery, the visual acuity was significantly better (P < .05) in patients treated with the eye tracker. The increase in coma-like (relative increase factor 0.4) and spherical aberrations (relative increase factor 1.1) was significantly smaller in these patients than in those in the nontracker group (spherical equivalents of 3.9 and 5.1, respectively; P < .05). The refractive outcome, however, was not significantly different in sphere and cylinder. Conclusion: The use of active eye tracking appeared to improve the optical and visual outcomes but did not affect the refractive outcome after photorefractive laser surgery.