Effect of monochromatic aberrations and wavelength on refraction and visual performance

Purpose. My doctoral studies examined how to transform monochromatic aberrations into a polychromatic model of visual performance. Methods. Using a patient's monochromatic aberrations, we conducted virtual refractions based on optimizing 30 metrics of optical quality. Virtual refractions were compared to subjective refractions that were determined to the nearest 1/8 diopter for defocus and astigmatism and incorporated a patient's depth of focus (DoF). Using a Badal optometer and a model of ocular chromatic aberrations, we psychophysically determined the wavelength of light that is optimally focused (WiF) on the retina when a white target is judged subjectively to be focused. After determining the WiF, we used each subject's monochromatic (843nm) wavefront aberrations and derived a model of polychromatic retinal image quality. Using this polychromatic retinal image model and a model of longitudinal chromatic aberration, we conducted virtual polychromatic refractions to predict the psychophysical WiF, the white light Badal refractions, and each subject's depth of focus. Results. A subjective refraction can be accurately predicted by a computational refraction utilizing objective metrics of optical quality. Accuracy and precision were improved if a multivariate approach was used and several metrics were combined to predict the subjective refraction. On average the WiF for a polychromatic light source is 565 nm. Subjective polychromatic refractions from NIR objective refractions can successfully be predicted with an accuracy comparable to the known test-retest accuracy of subjective refractions. The DoF is not strongly correlated with wavefront error. However, using an individual's wavefront aberrations and metrics of optical quality, a subject's depth of focus can be predicted utilizing Weber's Law, DeltaI/I, resulting in a quantity we call Thibos' constant. Conclusion. My doctoral studies advance monochromatic and polychromatic IQ analysis of the human eye. Predicting the subjective optimum focus is an important tool for improving methods of refractive correction. Determining the WiF can be used by others as the reference wavelength for polychromatic image modeling. Objectively quantifying the subjective depth of focus by applying Weber's Law has broad, wide-ranging applications: from academic research to outcome analysis of various modalities of refractive correction.