Wavefront- Guided Laser Surgery Many patients do not realize that the eye is an imperfect optical system. As light rays from distant objects pass through the individual optical components of the eye, they are subject to being distorted by the imperfections found in the cornea and the crystalline lens. The distortions that are created are referred to as "aberrations." The vast majority--90% or more--of these aberrations create common refractive errors, such as nearsightedness, farsightedness and astigmatism, which can be treated by optical devices, like glasses and contact lenses, or by Laser Vision Correction, using the conventional methods of LASIK, PRK or LASEK. The remaining 10% of optical aberrations create images which are altered by chromatic aberration, spherical aberration, diffraction, curvature of field, coma, trefoils and quadrafoils--collectively known as "higher order aberrations." These higher order aberrations only occur in a visually significant manner in 10% to 15% of the general population. When they do occur, they are entirely unique to a particular patient--much like a fingerprint. For these patients, the use of a wavefront-guided laser technique to create a completely customized reshaping of the surface of the cornea may be the best treatment option. To achieve a customized corneal shaping, it will require measuring the higher order optical aberrations using a wavefront analysis system called an aberrometer and then digitally interfacing it with a laser, using high speed computerized control to direct the delivery of a very tiny beam of laser energy across the cornea. The VISX Wavescan™ Wavefront System lets the surgeon see refractive aberrations in clear and accurate, rotating 3-D images. How does Wavescan™ do this? First, the Wavescan™ sends low-energy laser light into the eye. The light reflects off the retina and travels back through the lens and cornea as an outgoing wavefront. This wavefront is captured by the Wavescan™, which then measures it to determine both higher and lower order aberrations of the entire optical system. The aberrations are then displayed on-screen in precise 3-D images. To then create a customized corneal ablation from the aberrometer measurements we digitally interface that data with the VISX Star S4 Excimer Laser System. The VISX Star S4 Excimer Laser System incorporates the use of the ACTIVETRACK™, a high-speed computerized eye tracking method that helps the surgeon enhance your treatment by providing precise registration of the laser beam to create a customized ablation surface. Since your eyes are continually making very fine jumping movements - called "saccadic" movements which are beyond your control, no matter how hard you concentrate, the VISX Star S4 Excimer Laser System will assist the surgeon by scanning the eye. Then, using computer control, it makes micro-adjustments to reposition the laser beam between pulses of light, tracking even the smallest and quickest movements of your eye during treatment. The VISX Star S4 Excimer Laser System moves the laser beam across the surface of the cornea very rapidly in an overlapping pattern. This helps the surgeon deliver a smooth customized corneal shape to provide you quick visual recovery and an individualized correction of your prescription.