To evaluate the accuracy of the surgeon-selected ablation center in active eye-tracker-assisted ASA-PRK and to identify factors influencing the ablation center.

This retrospective study included 109 eyes of 62 patients who underwent active eye-tracker-assisted ASA-PRK (VISX STAR^TM S4 with ActiveTrak^TM System). The location the surgeon-selected ablation center and its distance from the center of the entrance pupil were analyzed by corneal topography (EyeSys Corneal Analysis System^TM with pupil finding software). The factors influencing centration were investigated.

The mean decentration was 0.24±0.13 mm (range 0.04 to 0.83 mm). One-hundred and five eyes (96%) were within 0.5 mm of the pupillary center. Supero-nasal displacement of the ablation center occurred most frequently in 44 eyes (40%) after ASA-PRK. The decentration amount was not dependant on factors related to the patient, the surgeon, or the surgery. There was no significant correlation between the amount of decentration and the vertical scale bar of the ActiveTrak^TM icon on the screen representing the distance from the pupil center determined by the tracking system, to the surgeon-selected ablation center.

This method of tracking the ablation center, which was selected by the surgeon according to each patient's specific pupil decentration with the active eye tracking system, was highly accurate and effective in avoiding severe decentration in ASA-PRK.