Purpose
To objectively define the effective centration of myopic femtosecond- laser assisted LASIK ablation pattern, evaluate the difference between achieved vs. planned excimer laser ablation centration, and compare these results from two different generations of an excimer laser system.
Methods
The study employed 280 eyes subjected to myopic LASIK. Digital image analysis was performed on Scheimpflug sagittal curvature maps (pre-operative, postoperative, and their difference). Centration was assessed via digital proprietary software analysis of the coordinate displacement between the achieved ablation geometric center and the planned ablation center, which was the corneal vertex. Results from two different excimer laser generations (Group-A, EyeQ 400 and Group-B, EX500), both platforms of Alcon/WaveLight were compared.
Results
Average radial displacement in group-A was on average 360±220 μm (range 0 to 1,030 μm), while in group-B 120±110 μm (range 0 to 580 μm). When comparing percentage of eyes with displacement more than 300 μm, in group-A the corresponding % was 52%, while in group-B, 4%, respectively.
Conclusions
Displacement of ablation pattern may depend on the laser platform. The dramatic improvement in the efficiency of centration indicates that newer generation excimer laser with faster eye tracking and active centration control appear to achieve a significantly more accurate centration of myopic ablation patterns. We propose this novel, objective technique for laser refractive surgeon evaluation that may point out significant outcome measures not currently used in standard metrics of refractive laser efficiency.
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