How plausible is it to treat a Decentered Ablation with AK?? Also, how can the center of an ablation be located on a Corneal Topography? Is the center of an ablation located in the flatest part of a Corneal Topography that corresponds with the least diopters power? Should the center of an ablation be loacted at the Visual Axis?

"Originally posted by FuzzyEyes:
How plausible is it to treat a Decentered Ablation with AK??"

Was this recommended to you? AK is to treat corneal astigmatism. If the de-centered ablation induced astigmatism, I don't know how predictable AK would be to treat it since the cornea would be asymmetric.

"Also, how can the center of an ablation be located on a Corneal Topography? Is the center of an ablation located in the flatest part of a Corneal Topography that corresponds with the least diopters power?"

Generally, yes. The center of the ablation is the flattest part, unless there is some irregularity at the very center. The center of the ablation is the center of the overall, induced profile change.

"Should the center of an ablation be loacted at the Visual Axis?"

Patients are asked to fixate on a light during the ablation procedure. This would attempt to center the ablation on the visual axis. The visual axis is not the same as the pupillary center or corneal center. The visual axis is, on average, about 1/2 mm nasal to the corneal apex. There is, or at one time was, a question about the centering of ablations over the visual axis versus the corneal apex. I don't know how even whether it was resolved.

The corneal apex is not exact relative to the visual axis. You may want to read the entire PDF listed at the URL below. The issue of visual axis (LOS) versus correction factors in wavefront aberrometry and ablation is discussed. One section discusses coma induction due to this very issue.

From the article: "Another important factor is the location of the comeal apex. The corneal apex is the point of the cornea that has greatest curvature. Mandell, Chiang and Klein8 showed that the location of the comeal apex relative to the pupil center varies across individuals. It is possible that meridional anisotropies of the transition zone are related to the location of the comeal apex."

(http://cornea.berkeley.edu/pubs/Proc_SPIE_4245-Problems...ractive_surgery.pdf)

Yes AK has been recommended recently. Thanks for all the info.