Higher-order aberrations produce orientation-specific notches in the defocused contrast sensitivity function

Local minima or notches in the defocused contrast sensitivity function (CSF) have been linked to the aberrations of the eye. We use theoretical modeling of the effects of the aberrations to show these notches can be orientation-selective due to the effects of aberration terms such as coma and trefoil. Notches that changed with orientation were observed in the defocused CSF of four subjects. The measured CSFs were found to match well with theoretical predictions produced using the individual aberrations. Theoretical modeling highlighted orientation-specific differences in notches for both positive and negative blur. The results indicate that orientation is an important variable when testing for the functional effects of higher-order aberrations.