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T. A. AlMahmoud, R. Munger, M. Lafontaine, S. Taylor, W. B. Jackson; Advanced Corneal Surface Ablation for Myopia Efficacy in Higher Order Aberrations Correction. Invest. Ophthalmol. Vis. Sci. 2009;50(13):587.
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© ARVO (1962-2015); The Authors (2016-present)
To compare the efficacy of four wavefront-guided advanced surface ablation (WF-ASA) techniques (AA-PRK, LASEK, Epi-PRK, Epi-LASIK) for treating high order aberrations (HOA) using STAR S4 IRTM (AMO) Excimer Laser system.
Ocular wavefront aberration (WaveScan WaveFrontTM System, AMO) and corneal topography (Pentacam, Oculus) of 240 eyes equally divided between the groups and matched for mean and range of required spherical correction (0.00 to -8.00 D) were obtained before and 3 months following WF-ASA. Corneal wavefront aberrations were calculated by ray-tracing from elevation maps using the ACAP software from AMO after registration of the corneal maps with the pupil center using the corneal apex to pupil center offset provided by the WaveScan aberrometer. Corneal and ocular aberrations were described as Zernike polynomials and analysis focused on spherical aberration (SA) and total HOA. All values and group comparisons were performed using One Way Anova’s and within group comparisons using paired t-tests. Correlations were performed using Pearson Correlations.
There was statistically significant (P<0.001 for all groups) surgically induced increase in SA in each of the groups at 3 months for both ocular (AA-PRK=0.10±0.08µm; LASEK=0.09±0.08µm; Epi-PRK=0.12±0.10µm; Epi-LASIK=0.12±0.08µm) and corneal analysis (AA-PRK=0.18±0.12µm; LASEK=0.17±0.19µm; Epi-PRK=0.17±0.13; Epi-LASIK=0.04±0.20µm). Total HOA also increased significantly in all groups following surgery both for ocular (AA-PRK=0.08±0.08µm; LASEK=0.06±0.10µm; Epi-PRK=0.07±0.11µm; Epi-LASIK=0.09±0.09µm) and corneal analysis (AA-PRK=0.23±0.18µm; LASEK=0.21±0.26µm; Epi-PRK=0.21±0.17µm; Epi-LASIK=0.07±0.37µm). There was no significant difference in the induced ocular SA and HOA between the four four ablation techniques but the differences in induced corneal SA and HOA were significant (P=0.010). Ocular change in SA were weekly correlated to preop SA (-0.30, P<0.001) but very strongly correlated to spherical correction (-0.68, P<0.001). Surgically induced corneal SA was weekly correlated to preop corneal SA (-0.34, P<0.001) and applied spherical correction (-0.46, P<0.001).
At 3 months all procedures resulted in an increase in HOA and SA. The amounts of induced aberrations were most strongly correlated to the applied spherical power treatment and not the preoperative aberration level.
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