Examination of Visual Performance by Adaptive Optics

Background: The dependence of visual quality on higher order aberrations (HOA) is highly important for refractive surgery (LASIK) as well as for the correction by vision aids. The use of the adaptive optics (AO) enables the measurement and manipulation of conventional lower order aberrations (defocus, astigmatism) and for HOAs as well. In this work, an Adaptive Optics Visual Simulator is presented that enables one to correct wave-front deformations up to the sixth order of Zernike polynomials, as well as to induce specific aberrations. The subjects observe a TFT monitor, so that a subjective rating of the visual impression is possible, as well as objective measurements. Methods: Possible applications of such an adaptive optics visual simulator are demonstrated by means of several studies in this survey paper. The main challenge was to investigate the influence of HOAs on the subjective visual impression. Thereby, the following questions have been examined among others: Does the correction of the HOAs lead to an improved visual impression? Are there ways to check the effect of HOAs, what are the effects of single HOAs on the subjective visual impression and what just-noticeable levels do they have? Results: Three studies are presented investigating the impact of HOAs on visus, contrast sensitivity and on vision with glare as well as objective stimulus thresholds of selected HOAs. For example, by using a staircase-procedure it was possible to determine that the objective stimulus threshold for coma has a significantly lower value than the thresholds for astigmatism or trefoil. Conclusion: Adaptive optics enables the investigation of effects of HOAs on subjective and objective visual impression. In future, this may result in individualised corrections of refractive errors, which will improve the patients quality of life.