Wavefront Technology: What is it?
Jennifer Kimberley
When LASIK was first approved by the Food and Drug Administration (FDA) it was not a Wavefront-guided procedure. That non-wavefront procedure is now usually called Standard LASIK or Traditional LASIK, because Wavefront-guided LASIK has succeeded it.
Diagnosis Before Treatment
Traditional LASIK diagnoses the eye’s refractive error using a phoropter. That is the same instrument used by ophthalmology offices when testing you for a new prescription. As you look into its eyepiece you see the vision chart with the rows of letters. The doctor switches from lens to lens asking you which gives clear vision of the letters. “What is the lowest row you can read?” That procedure zeros in on what strength of lens gives you clearest vision.
It measures only two corneal abnormalities:
- Cylindrical – causing astigmatism
- Spherical – causing nearsightedness and farsightedness
Wavefront-guided LASIK diagnoses the eye’s refractive using a computerized system that gathers more extensive and subtle information about your eyes. Your treatment is then based on this detailed information, giving you a more precise vision correction.
There are four FDA-approved Wavefront LASIK systems:
- The LADARVision CustomCornea – also by Alcon Laboratories, Inc.
- The Technolas 217z Zyoptix by Bausch & Lomb Surgical, Inc.
- The AMO VISX S4 CustomVue – originally by VISX, Inc., but in May,2005, VISX was acquired by Advanced Medical Optics, Inc.
- The Allegretto Wave Excimer Laser System – by WaveLight AG
Refractive Error
There are two types:
- Lower order aberrations – namely, myopia, hyperopia and astigmatism. These are tested when you go to the eye doctor’s office for glasses or contact lenses.
- Higher order aberrations – of which there are dozens, and more being discovered all the time by these wavefront systems. Some examples are starbursts and halos around light sources, and double vision where there’s a pale “ghost” duplicate image when you look at each object around you. Many have no names yet, but are just mathematical formulations.
Some of the higher-order aberrations are sometimes side effects of a Standard LASIK procedure, at least temporarily. A big advantage of having a Wavefront-guided procedure instead of a Standard procedure is the greater chance of not having such side effects. That is because your treatment is more precise and customized, taking your higher order aberrations into account for the treatment plan.
The Wavefront-guided LASIK systems all diagnose the eye’s higher order aberrations, as well as the lower order aberrations.
How Does Wavefront Diagnosis Work?
While you focus on a target through the system’s eye piece, a laser is directed into the eye. Laser beams are parallel and straight. When that light reflects back from your eye to the system’s sensor, it is no longer parallel or straight, but has a changed configuration at the front end (the “wavefront”). The changes express that eye’s refractive error.
In other words, the tiny deviations from “parallel and straight” are caused by tiny irregularities in the eye. The light has reflected back through the lens and cornea to the system’s sensor, and by the time it arrives, it has been distorted by the irregularities of those eye structures.
Basis of Your Treatment Plan
The Wavefront system computer creates a 3-D map from the information brought to it by the reflected light. Your LASIK surgeon studies these two maps, one for each eye, to determine how corneal tissue should be modified to improve your vision. Since the treatment laser is part of the Wavefront system, the digital information can guide its movements in your treatment. However, the computer and whole Wavefront system are under the control of your eye surgeon, who could stop treatment at any moment if that were necessary.
For more information on LASIK, please see the links on our Ophthalmology and LASIK Articles page. If you would like to arrange for a personal consultation with a qualified LASIK surgeon in your area, please see the list of states below.
