Study favors centering ablation profile over vertex

June 15, 2008

Centering the corneal ablation profile over the corneal vertex when treating hyperopia using an excimer laser platform (Schwind Esiris, Schwind eye-tech-solutions) results in better visual outcomes compared with ablations that were centered over the pupil centroid.

Key Points

Dr. El-Kateb and colleagues conducted a study to evaluate the visual effect of ablations centered over the corneal vertex in patients with hyperopia compared with ablations centered over the pupil centroid. The rationale for the study was to determine a difference in approaches because, Dr. El-Kateb said, all excimer laser ablations are centered on the pupil centroid.

Determining center of ablation

The method used in this study to determine the center of the ablation on topography was the circle difference, in which a transparency with multiple concentric circles is placed atop the difference map and a cursor is placed in the center, he said.

Analysis of the safety data indicated that centering the ablation over the corneal vertex resulted in a more beneficial visual outcome.

"Excellent centration of hyperopic correction is possible in eyes with a positive angle kappa when the ablation is centered over the corneal vertex. Further studies are needed with a larger number of patients and longer follow-up periods to confirm our results," he concluded.