[Optical and physiological limits of wavefront-controlled keratectomy].

According to optical diffraction theory, a visual acuity of 20/3.5 is possible in human eyes with pupil diameters larger than 6 mm. This theoretical value cannot be obtained in practice - in fact visual acuity is limited by the scale of the mosaic of the retinal cones. Anatomical data and the model by Helmholtz-Hering suggest that visual acuity of humans cannot be substantially higher than 20/10. Many young adult reach this visual acuity with their normal spectacles or contact lens correction. The human eye has higher-order aberrations which can be measured with a Hartmann-Shack aberrometer. A partial correction of these aberrations is possible by means of wavefront-controlled keratectomy and customized corneal ablation. A perfect eye completely free of ocular aberrations cannot be created by customized refractive surgery as, for example chromatic aberration cannot be corrected and the strength of ocular aberrations depends on the state of accomodation and varies with time.