Influence of corneal topography on higher order aberrations in myopic astigmatic patients

Objective To investigate the distributive feature of higher order aberrations in myopic astigmatic patients and to analyze the influence of corneal topography on it.Methods 434 eyes of 281 patients were objectively measured with wavescan wavefront system before laser in situ keratomileusis (LASIK) treatment.Corneal surface regularity index (SRI),surface asymmetry index (SAI) and corneal shape were obtained by Tomey Corneal Topography (TMS-4).Correlated analysis was performed between refractive power,SRI,SAI and the root mean square (RMS) of higher order aberrations,respectively.Enrolled eyes were divided into 5 groups by corneal shape.Rank run test was performed to compare the RMS within groups.Results The RMS of higher order aberrations (RMSh) was (0.286±0.098)μm and decreased from third to six order aberrations across a 6.0mm pupil.Among these aberrations,the main comments were 3rd order coma,trefoil and 4th order spherical aberrations.The refractive power and SRI had no significant correlation with RMSh,Whereas,SAI had positive correlation with RMSh.Pearson coefficient was 0.161 and P=0.001.SAI had more influence on higher order aberrations than SRI.RMSh increased with SAI especially when SRI was low,and the main increase was 3rd coma and 4th spherical aberrations.More RMSh was shown in the irregular pattern and asymmetry bow tie pattern than the other corneal shapes,and the main increase was trefoil and 3rd coma.Conclusion With a pupil diameter of 6.0mm,the main high order aberrations of myopic astigmatic patients are 3rd coma,trefoil and 4th spherical aberrations.More RMSh is shown in the irregular pattern and asymmetry bow tie pattern than the other corneal shapes.SAI has more influence on the higher order aberrations than SRI.