The Effects of Fixation Ring on Corneal Centration in LASIK Using Flying Spot Laser

ABSTRACT

PURPOSE: To compare the accuracy of centration of ablation zones and visual acuity with two different techniques (fixation ring and patient self-fixation) with flying spot laser to maintain immobilization of the globe during laser assisted in situ keratomileusis (LASIK). METHODS: 240 eyes from 124 patients who underwent LASIK by two techniques were studied retrospectively. One technique used a fixation ring to maintain centration of the cornea and the other technique used patient fixation, with no mechanical restraint of the eye. The eyes were treated with the MEL-70 flying spot excimer laser and topographic maps were recorded with the ATLAS(R) (MasterVue(R) software, Zeiss Humphrey, Germany). The amount and direction of decentration were compared between the 2 techniques. The preoperative and postoperative best corrected visual acuity were also compared. RESULTS: Mean amount of decentration in fixation ring using group was 0.59+/-0.39 mm and that of decentration in patient fixation group was 0.61+/-0.42 mm. Between the two groups, no significant difference in amount of decentraion was noted statistically. Most of decentration from the pupil center was located superonasally and inferonasally. Also there was no difference in the mean preoperative best corrected visual acuity, spherical equivalent, 1 year postoperative best corrected visual acuity between the two groups. CONCLUSIONS: The fixation ring during LASIK makes no difference with patient self-fixation in amount of decentration of ablation zone in spite of relatively long time of laser shot in flying spot excimer laser.