Just-Noticeable Levels of Aberration Correction

Abstract

Purpose The objectives of this study were to determine whether the correction of higher-order aberrations (HOA) would be detectable by “normal” subjects and whether a full correction is necessary or better than a partial correction of the main HOA (i.e., spherical aberration (SA), coma and trefoil). Methods Three subjects made side-by-side comparisons between an uncorrected aberrations image (i.e., including typical HOA) and partially corrected variant images in order to determine which image was subjectively preferred. Results The subjective preference was found to be well correlated (r 2=0.84) with the volume under the modulation transfer function (VMTF). A significant difference of subjective preference was found with change of SA correction ( P=0.014) and with change of coma correction ( P=0.009) but not with the correction of trefoil ( P=0.133). Changing the VMTF by less than 6.3% did not induce a perceptible difference (i.e., subjective preference higher than 25%) whereas changing the VMTF by more than 10% often induced a perceptible difference. Moreover, based on the through-focus subjective preference curve, we obtained a just-noticeable level of defocus of 1/8 D. Conclusions The subjective quality of vision of a subject with typical aberrations could be improved by either a partial (50%) or a full correction of both SA and coma, this gain being comparable to 1/8 D of defocus blur. However, the effect of the correction of the trefoil appears negligible. The VMTF is a good image quality metric to predict subjective preference. A perceptible difference in image quality can be obtained by changing the VMTF by 6.3 to 10%.