Abstract
Abstract: :
Purpose: To evaluate the ablation centration after LASIK using the VISX Star S3 with Active Trak versus the VISX Star S2 in myopia and myopic astigmatism. Methods: The corneal topography (Keratron Corneal Analyzer) of seventy-one consecutive VISX StarS3 with Active Trak treated-eyes and 71 VISX StarS2 treated-eyes were retrospectively analyzed at post-op month 3 for centration ablation. Myopia ranged between –1.50 and –11.25 (D) and cylinder was between +0.25 and +2.75 (D). All StarS3-treated eyes were matched with StarS2-treated eyes having sphere within 0.5 D and cylinder within 0.25 D. Of these, 79 eyes had data permitting evaluation of ablation. Decentration from the pupil center was read off in millimeters and angle of semimeridians, after placing the computer cursor at the center of apparent ablation with the aid of a transparent grid placed over the computer screen. Results: Mean decentration of the ablation from the pupil centers was 0.18 mm 0.13 in StarS3 eyes (n=45) and 0.21 0.10 in StarS2 eyes (n=34), p=0.24. No eye in either group had significant decentration, defined as displacement from the pupil center by 0.5 mm or more. Meridional displacement occurred between 80 and 90 degrees in 93% of S3 eyes and in 90% of S2 eyes (p=0.65). Only two eyes in the S2 group lost 2 lines of BSCVA at postop month 3—decentrations were 0.13 and 0.24 mm in each eye. Conclusion: Comparable ablation centration can be achieved both with and without active eye tracking during LASIK.
Keywords: 546 refractive surgery: comparative studies • 547 refractive surgery: corneal topography • 548 refractive surgery: LASIK