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L. Wang, D.D. Koch; Fitting Methods for Calculating Changes in Corneal Wavefront Aberrations: Best–Fit–Sphere or Plane Reference? . Invest. Ophthalmol. Vis. Sci. 2006;47(13):581.
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© ARVO (1962-2015); The Authors (2016-present)
To compare different fitting methods for calculating corneal wavefront aberration changes.
In 114 eyes of 69 patients who underwent myopic LASIK, ocular wavefront aberrations before and after the surgery were measured using the VISX WaveScan system. Changes in aberrations induced by the surgery on the anterior corneal surface were calculated using 3 references: 1) device–selected best–fit–sphere (BFS) for pre– and post–op corneas, 2) plane reference for both pre– and post–op corneas, and 3) pre–op cornea BFS for both pre– and post–op corneas.
For defocus (Z20), coefficient changes on the anterior corneal surface calculated with the plane reference (–4.88 ± 2.44 µm) and the pre–op corneal BFS (–4.78 ± 2.39 µm) were similar to the change in whole eye (–4.79 ± 2.51 µm). In contrast, coefficient changes on the anterior corneal surface calculated with device–selected BFS (0.20 ± 0.58 µm) were significantly different from the change in whole eye (P<0.001). Differences also existed for some higher–order Zernike terms. There were no differences between methods for lower–order astigmatism terms.
When investigating surgically induced wavefront aberration changes on the corneal surface, a plane reference or the same BFS (e.g., BFS for pre–op cornea) should be used for corneas before and after the procedure.
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