Study supports centering ablations on the visual axis

This retrospective study found no significant difference in refractive outcomes or night vision disturbances after moderate to high hyperopic LASIK centered on the coaxially sighted corneal light reflex (CSCLR) between eyes with a small and large angle kappa. This supports the notion that centration relative to the CSCLR may be preferable to systematic alignment with the pupil center.

This study’s findings may have broader implications for corneal and lens-based refractive surgery as a whole and could be an important consideration for intraocular lens alignment, particularly with multifocal lens implantation.

In corneal refractive surgery, it is imperative to have a well-centered ablation in order to achieve optimal visual results. A decentered treatment can lead to a significant increase in higher-order aberrations, decreased quality of vision, diplopia, decreased contrast sensitivity, and night vision disturbances. However, there is still some disagreement over where best to center the corneal ablation: on the entrance pupil center (line of sight) or on the corneal vertex (approximate proxy for the visual axis). There are proponents for both sides of the argument, and the standard protocol for corneal excimer laser ablation centration for the U.S is against the entrance pupil center.

Investigators retrospectively compared outcomes of moderate to high hyperopic LASIK using the MEL80 excimer laser between eyes with a small (< 0.25 mm pupil offset) versus a large (> 0.55 mm pupil offset) angle kappa. All ablations were centered on the CSCLR using the standard nonwavefront–guided ablation profile.

At 12 months of follow-up, there was no difference in refractive outcomes, accuracy, induced astigmatism, contrast sensitivity or night vision disturbances.

They write that the results of this study may only apply to hyperopic treatments using the MEL80 excimer laser, although similar results have been reported using other excimer laser systems when the treatment has been centered on the CSCLR or corneal vertex.