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Anatoly Fabrikant, Dimitri Chernyak; Analysis of Wavefront and Corneal Topography Changes due to Laser Refractive Surgery. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5756.
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Laser refractive surgery often struggles with unintended side effects, including some low-order and high-order induced aberrations. Analysis of induced aberrations requires comparison of actual cornea changes vs. intended ablation. We need to analyze deviations of actual ablation from the intended ablation in order to understand the root cause of treatment errors and adjust the treatment planning algorithm accordingly.
We performed a statistical analysis, based on clinical data from low to moderate myopes (173 eyes). All data sets included pre- and post-operational wavefront and topography measurements. The intended treatment was computed with an AMO algorithm, based on a pre-operational wavefront measurement. Post-operational measurements were averaged over multiple treatments. Paired pre- and post-operational corneal topography measurements provided a measure of actual ablation performed during laser surgery. The actual ablation was compared with the intended ablation, computed from a pre-operational wavefront measured for the same eye, and also with the paired pre- and post-operational wavefront.
The topography and wavefront changes both in spherical aberration and coma appeared well correlated - see Fig. 1. Fig.1. Changes in spherical aberration (dSA Topo) and X,Y components of coma (dCM Topo) for corneal anterior surface vs. wavefront (dSA_WFpost-WFpre, dCM_WFpost-WFpre) for 173 eyes with 6mm diameter optical zone and periods from 1M to 9M.
The correlation of aberration changes in anterior cornea surface with the wavefront change, caused by laser ablation, shows that it is mainly the changes in anterior corneal surface that induce high-order aberrations. Post-operational changes in the eye interior structure (if any) make little effect on the aberrations.
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