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N. H. Siegel, W. M. Munir; Variation in Corneal Wavefront Aberrations by Calculation Method. Invest. Ophthalmol. Vis. Sci. 2010;51(13):5656.
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© ARVO (1962-2015); The Authors (2016-present)
To compare corneal wavefront aberrations, including 3rd, 4th, 5th, and 6th order in addition to total higher order aberrations (HOAs) and spherical aberration (SA), between the Nidek Magellan corneal topographer (NIDEK Co., Ltd, Japan) and VOL-CT software (Sarver and Associates, Inc., Illinois).
Data was collected prospectively for patients without existing corneal disease prior to undergoing cataract surgery. Corneal HOAs were calculated using Zernike polynomial expansions from corneal topographic data using both the built-in Nidek Magellan software and VOL-CT software. The preoperative data was calculated using both 4 and 6 mm pupil sizes. Calculations were corrected for pupil centration.
Corneal topography data was analyzed for 22 patients. The Nidek calculations were, for the most part, greater than the VOL-CT calculations. There were statistically significant differences between the two calculations for 4th, 5th, and 6th order aberrations using two-tailed paired t-tests. For 4th order aberrations using a 4 mm pupil size there was a statistically significant difference (Nidek: 0.287, VOL-CT: 0.146, P = 0.0457). There are statistically significant differences in 5th and 6th order corneal wavefront aberrations using a 6 mm pupil size (5th order: Nidek 0.312, VOL-CT 0.207, P = 0.0120, and for 6th order: Nidek 0.259, VOL-CT 0.108, P = 0.0046). There were no statistically significant differences for 3rd order, SA, and total HOAs at either pupil size. However, using 4 mm pupil size, the sign for SA differed for 2 out of the 22 total patients and using 6 mm pupil size, the sign differed for 5 out of the 22 total patients.
There are statistically significant differences in wavefront aberration calculations using the Nidek topography software versus the VOL-CT software both for the 4 and 6 mm pupil sizes. Such differences can include positive versus negative sign changes in SA, which could influence wavefront optimized intraocular lens selection for cataract surgery. Further study is needed to elucidate the variation in corneal wavefront aberrations based on calculation method and to determine more consistent standards for reliable comparison.
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