Role of Adaptive Optics in the Recent Management of Higher Order Aberrations in Laser Corneal Ablations

Abstract

The eye, like any other optical system, suffers from a number of specific optical aberrations. The optical quality of the eye is limited by optical aberrations, diffraction and scatter. (Cerviño et al., 2007) Our understanding of the optical system of the eye is evolving quite rapidly due to the combined effort of new experimental methodologies and advanced modeling. (Navarro, 2009) Imperfections in the components and materials in the eye may cause light rays to deviate from the desired path. These deviations, referred to as optical aberrations, result in blurred images and decreased visual performance. (Schwiegerling, 2000) Basic data regarding corneal and ocular wave front aberrations, such as distribution in the population and changes with aging, are essential for understanding the nature of each aberration and correcting it. (Oliveira et al., 2012) While lower-order aberrations include common aberrations like defocus (e.g., nearsightedness and farsightedness) and regular astigmatism, higher-order aberrations may include secondary astigmatism, spherical  Introduction 2 aberration, coma, trefoil, and quadrafoil stemming from irregular deformations, stress lines, and scarring on the corneal surface. (Sawides et al., 2012) These lower order aberrations (LOA) are normally corrected with spectacles or contact lenses, the ultimate challenge is the customization of the correction by compensating for HOA. These are typically uncorrected and thus chronically expose the visual system to optically blurred images. (Sawides et al., 2012) Zernike polynomials are representations of the higherand lower-order aberrations of the cornea, allowing a mathematical approach to their determination. (Bass et al., 2010) Recent technical innovations such as wavefront sensing and adaptive optics (AO) have allowed researchers for the first time to precisely quantify the complex optical system that is the human eye and attempt to control the retinal image with unprecedented sophistication. (Rossi et al., 2007) Adaptive optics is the technology permitting the manipulation of the aberrations, and eventually their correction, it is a technology used to improve the performance of optical systems by reducing the effect of wavefront distortions. (Bass et al., 2010).