The basics of wavefront aberrometry

Abstract

AbstractWavefront technology has been first used by astronomers for years in order to reduce higher order aberrations induced by the earth’s atmosphere, it has been introduced into clinical eye care recently.<br /> Ophthalmological practice involves performing a full subjective refraction. The sphere, cylinder and axis of astigmatism are measured. We are only correcting two components of a whole host of refractive components of the optics of an eye. These two components (sphere and cylinder) constitute by far the majority of the optical aberration of an eye. <br /> Even a basic exam yields important information about optical quality. However, all ophthalmologists have been faced with patients reporting visual acuity (or contrast sensitivity, glare, etc.) at levels much lower than would be expected from an eye exam.<br /> Wavefront aberrometry measures aberrations over the entire eye taking into account not only spherocylindrical refractive error, but also spherical aberration, trefoil, coma, secondary astigmatism as well as other “higher order” aberrations described by Zernike polynomials. Higher order aberrations are thought to contribute to more than 20% of the total number of aberrations in a normal eye an increase with pupil size. In the majority of normal patients, these high order aberrations play a minor role, however, in cases of refractive surgery, keratoconus and orthokeratology, they can induce a number of visual disturbances. <br /> We will define higher‐order aberrations and show how to measure them, giving you a basic working knowledge of wavefront sensing (also known as aberrometry). <br /> We will show how wavefront sensors work, what are Zernike polynomials, what they tell us and we will show present and future clinical applications of wavefront aberrometry.