New asymmetric centration strategy combining pupil and corneal vertex information for ablation procedures in refractive surgery: theoretical background.
OBJECTIVE
To describe a method for centering ablation profiles considering pupil center and corneal vertex information simultaneously.


METHODS
Novel ablation profiles were developed to cover the pupil aperture while respecting the corneal vertex as the optical axis of the ablation (asymmetric offset [AO]). The approach has been extended to combine higher order aberrations (HOA) referred to the pupil center (line-of-sight) with manifest refraction values referred to the corneal vertex (visual axis). The shapes and sizes of ablation profiles planned with AO were compared with the shapes and sizes of "classic" ablation profiles (with symmetric offset and without [no] offset, respectively).


RESULTS
The introduction of asymmetric offset leads to an asymmetric ablation profile that is virtually the same depth as no offset ablation profiles (symmetric offset profiles ablate deeper), with the same diameter as no offset ablation profiles (smaller than symmetric offset ablations). The ablation volume of AO profiles lies between the ablation volumes of no offset and symmetric offset ablation profiles. When combined with HOAs, AO ablation profiles affect specific HOA terms. Asymmetric offset spherical components affect HOA coma components, and AO astigmatic components affect HOA trefoil components.


CONCLUSIONS
Asymmetric offset ablation profiles provide a simple method to combine pupil and corneal vertex information for ablation procedures in refractive surgery with the optical axis of the ablation lying on the visual axis and the edges of the optical zone being concentric to the pupil boundaries. Further clinical studies must be performed to support the theoretical results.
SCHWIND eye-tech solutions, Kleinostheim, Germany. samuel.arba.mosquera@eye-tech.net
Samuel
S
Arba Mosquera
Tobias
T
Ewering
D048988:Corneal Surgery, Laser / Q000379:methods*; D057108:Corneal Wavefront Aberration / Q000503:physiopathology*; D006801:Humans; D008962:Models, Theoretical; D011680:Pupil / Q000502:physiology*; D012029:Refraction, Ocular / Q000502:physiology*