High-order Aberration In Eyes Of Young Adults With Myopia Measuring By ITrace Visual Function Analyzer

[ Objective ] To investigate the distribution of ocular and corneal high-order aberrations (HOAs, 3^rd to 6^th orders) in myopic eyes of young adults, by using the iTrace Visual Function Analyzer, and study the changes as a function of the degree of myopia.[Methods] Using the iTrace Visual Function Analyzer, root mean square(RMS)of total HOAs, 3^rd-,4^th-,5^th-,6^th-order aberrations, and coma (Z₄⁰, Z₆⁰) , SA (Z₃^-1, Z₃¹, Z₅^-1, Z₅¹) of the ocular, corneal, and internal aberrations were computed from the central 6.0mm and 4.0mm zone respectively of 420 eyes of 104 subjects (age 16 to 24 years), which simultaneously measured refraction. Correlation analysis was performed to assess the association between HOAs and refractive power, HOAs and pupilar diameter, and the aberration symmetry between the right and left eyes.Compensation factor(CF) was computed to assess how internal optics compensate for anterior corneal aberration.[Results](1) The mean of the ocular and corneal total high order RMS(3^rd to 6^th) was 0.433±0.176μm and 0.413±0.134μm respectively (pupilar diameter=6mm). The values of Zernike coefficients progressively decreased from the 3^rd-order to the 6^th-order (except Z₄⁰). The mean coefficient of the 4^th-order SAs(Z₄⁰) was 0.272±.086μm and was positive in all corneas.(2) High correlations were found between total ocular high order RMS and myopia, as well as coma (p<0.01) , while the SAs and (Z₄⁰) were stable. No correlation was found between total corneal high order RMS and myopia. However, horizonal primary coma(Z₃¹) was found statistically significant correlate with spherical equivalent (SE)(p<0.01) .(3) The total ocular high order RMS values at least doubled for 89% subjects when the pupil dilates from 4 to 6mm. For dilated pupils, the linear regression between aberration and myopia is steeper. SA occurs more frequently as pupil larger.(4) The total HOAs, SA and coma were moderately correlated between the right and left eyes( r=0.569, r=0.672 and r=0.418, respectively, all p<0.002). Overall, 9 of the 22 Zernike terms (41%) were significantly correlated between the right and left eyes. The strongest correlation was found for the 4^th-order SA(Z₄⁰) (r=0.72,p<0.002).(5) The CFs varied widely among subjects. The negative values of internal SA compensated for the positive S A of cornea. For eyes with low whole-eye RMS values, mean RMS for the anterior cornea was greater than that for the whole eye. However, for eyes with larger whole-eye RMS values, the RMS values of the anterior cornea were less than that for the whole eye. Internal optics made important contributions to the wave-front aberrations for higher-order aberrations. in the whole eye[Conclusion] The wavefront aberrations varied greatly among young adults. High correlations were found between total ocular high order RMS and myopia. SA occurs more frequently as pupil larger. Moderate to high correlations were found between the right and left eyes .Internal surfaces compensated at least partially for the HOA and Z₄⁰ in most eyes.