Wave aberration of human eyes and new descriptors of image optical quality and visual performance

The expansion of wavefront-sensing techniques redefined the meaning of refractive error in clinical ophthalmology. Clinical aberrometers provide detailed measurements of the eye's wavefront aberration. The distribution and contribution of each higher-order aberration to the overall wavefront aberration in the individual eye can now be accurately determined and predicted. Using corneal or ocular wavefront sensors, studies have measured the interindividual and age-related changes in the wavefront aberration in the normal population with the goal of optimizing refractive surgery outcomes for the individual. New objective optical-quality metrics would lead to better use and interpretation of newly available information on aberrations in the eye. However, the first metrics introduced, based on sets of Zernike polynomials, is not completely suitable to depict visual quality because they do not directly relate to the quality of the retinal image. Thus, several approaches to describe the real, complex optical performance of human eyes have been implemented. These include objective metrics that quantify the quality of the optical wavefront in the plane of the pupil (ie, pupil-plane metrics) and others that quantify the quality of the retinal image (ie, image-plane metrics). These metrics are derived by wavefront aberration information from the individual eye. This paper reviews the more recent knowledge of the wavefront aberration in human eyes and discusses the image-quality and optical-quality metrics and predictors that are now routinely calculated by wavefront-sensor software to describe the optical and image quality in the individual eye.