Topographical Analysis of Ablation Decentration Between Eye Tracker-assisted and Unassisted LASIK

Choi, Si Hwan; Kim, Yong Sun; Yim, Jin Ho

Abstract

PURPOSE: This study was aimed to evaluate the efficacy of an eye-tracking system, in terms of the amount of decentration. Comparison was made between two LASIK groups operated with and without the use of eye-tracking system.
METHODS
An eye-tracking system was used in 41 eyes(Group 1) and patient fixation alone without an eye-tracking system in 41 eyes(Group 2). Corneal topography(Humphrey ATLAS(TM) Corneal Topography System; Zeiss Humphrey Systems, Dublin, California, U.S.A.) was performed before surgery and 3 months postoperatively. The amount of ablation decentration was measured on the difference map obtained from the axial map.
RESULTS
The mean +/-SD of decentration was 0.38 +/-0.23 mm in group 1, and 0.49 +/-0.24 mm in group 2(p=0.047). The amount of decentration was graded as follows: grade I(<0.5 mm); Grade II(0.5~1.0 mm); Grade III(>1.0 mm). Grade I, there was a significantly less decentration in group 1(p=0.037). For grade II, however, there was no significant difference between the two groups(p=0.766).
CONCLUSIONS
Using eye-tracking system alone may not be effective in decreasing moderate decentration. Good fixation of the patients seemed to be as effective as an eye tracking system in achieving good ablation centration.