Neural compensation for the eye’s optical aberrations

Abstract

A fundamental problem facing sensory systems is to recover useful information about the external world from signals that are corrupted by the sensory process itself. Retinal images in the human eye are affected by optical aberrations that cannot be corrected with ordinary spectacles or contact lenses, and the specific pattern of these aberrations is different in every eye. Though these aberrations always blur the retinal image, our subjective impression is that the visual world is sharp and clear, suggesting that the brain might compensate for their subjective influence. The recent introduction of adaptive optics to control the eye's aberrations now makes it possible to directly test this idea. If the brain compensates for the eye's aberrations, vision should be clearest with the eye's own aberrations rather than with unfamiliar ones. We asked subjects to view a stimulus through an adaptive optics system that either recreated their own aberrations or a rotated version of them. For all five subjects tested, the stimulus seen with the subject's own aberrations was always sharper than when seen through the rotated version. This supports the hypothesis that the neural visual system is adapted to the eye's aberrations, thereby removing somehow the effects of blur generated by the sensory apparatus from visual experience. This result could have important implications for methods to correct higher order aberrations with customized refractive surgery because some benefits of optimizing the correction optically might be undone by the nervous system's compensation for the old aberrations.

Calculations and Measurements of the Visual Benefit of Correcting the Higher-order Aberrations Using Adaptive Optics Technology

“…Recent studies 7,8 have suggested that we might be adapted to our retinal image, which would have an impact on the visual benefit of correcting the eye's aberrations. Artal et al 7 wondered whether the visual system was adapted to the retinal image of its own eye; in other words, is the best overall subjective image quality obtained when a perfect retinal image is presented on the retina or when the retinal image is blurred by the aberrations of the eye's optics, indicating that the neural system is adapted to the particular pattern of its own eyes, and is able to compensate for the effects of this blur.…”

Tissue-Saving Zernike Terms Selection in Customized Treatments for Refractive Surgery

“…9 Finally, the concept of neural compensation suggests that the neural visual system is adapted to the eye's own aberration pattern. A study by Artal et al 10 on the effects that this neural compensation causes on the visual function indicates that the visual quality we have is somewhat superior to the optical quality that our eye provides.…”

Modeling of a Magnetic-Fluid Deformable Mirror for Retinal Imaging Adaptive Optics Systems

“…The enhanced capability has facilitated developments such as identification of the arrangement of the three classes of photoreceptor cells (Roorda and Williams 1999), psychological testing of the functioning of vision at the neural level (Artal et al 2004), and finding of alternate causes of color blindness (Carroll et al 2004). One of the most promising applications of AO systems in ophthalmology is optical coherence tomography (OCT) which provides depth resolution, allowing clinicians to visualize different retinal layers (Zhang et al 2005).…”