Abstract
Recently there has been increasing effort in developing single-value ocular optical quality metrics that can be derived from increasingly popular aberrometry. The ultimate goal is to use one or more of these objective metrics to predict visual performance with wavefront aberrations accurately and precisely. To this end, it's necessary to evaluate many metric candidates for different situations so that the final standouts can be picked out. The purpose of this study was to evaluate optical transfer error as such a metric in post-LASIK eyes.
The metric optical transfer error (OTE) takes into account the phase variability of the optical transfer function (OTF) of the eye by analyzing the gradient profile of the eye's OTF, which in turn can be derived from wavefront aberrations at the pupil plane. Post-LASIK visual performance measures (high contrast logMAR and low contrast logMAR) and wave aberrations for a cohort of young pilots were obtained in the US Army Aeromedical Research Laboratory. OTE and RMS were calculated for up to 4th, 5th and 6th Zernike terms as specified by the OSA convention. The predictability of the four visual acuities with OTE and RMS were then analyzed.
Similar to RMS, OTE fails to predict any of the post-LASIK visual performance measures. Though OTE was originally shown to be a better optical quality metric than RMS for simple combinations of Zernike terms, it is highly correlated with RMS when complicated combinations of Zernike terms are present in these post-LASIK eyes.