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K. M. Bottos, J. B. Ko, M. A. Isidro, N. Wongpitoompyia, N. H. O. Camara, M. T. Leite, T. Purcell, D. J. Schanzlin; Corneal Asphericity and Spherical Aberration Changes After Refractive Surgery as a Function of Central Ablation Depth and Refractive Status. Invest. Ophthalmol. Vis. Sci. 2010;51(13):3940.
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Purposes: To analyze corneal asphericity (Q) and spherical aberrations (SA) after refractive surgery and their relationship with refractive status and central ablation depth.
Our retrospective study comprised 160 eyes of 90 patients with myopia or myopic astigmatism who underwent refractive surgery from January 2008 to November 2009. All the subjects were treated with the aim of plano correction and achieved uncorrected visual acuity of 20/20 or better. Only reliable Pentacam (Oculus, Wetzlar, Germany) measurements were considered. Pupil pachymetry, corneal asphericity (Q) values and corneal wavefront spherical aberration (SA) Zernike values using a 6 mm optical zone were obtained. Mean age was 35 (+/- 9.3 years), 73 were men (45.62%) and 87 were women (54.37%).
Mean preop Q value was -0.23 ± 0.25 (SD) and mean postop Q value was +0.28 ± 0.46 (Delta Q = +0.51 ± 0.46). Regarding the SA, mean preop was +0.20 ± 0.07. Mean postop SA was +0.31 ± 0.18 (Delta SA = +0.11 ± 0.19) and ranged from +0.03 to +1.00. Changes in asphericity (Delta Q) and corneal SA (Delta SA) after the surgery were highly correlated with the preop spherical equivalent (P<0.001) and ablation depth (P<0.001). There is a tendency of both Q value and SA to become more positive after a myopic correction.
From our study we found myopic correction induced a positive change on both Q value and corneal SA. The higher the myopic refractive status preoperatively and the greater the ablation depth, the more positive the SA and Q value after ablation.
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