During a conventional treatment procedure the glasses prescription is corrected. A typical glasses prescription corrects approximately 90% to 95% of the refractive error. The remaining percentage of the refractive error cannot be corrected with glasses because it is comprised of irregularities within the visual system.
However, with a custom LASIK procedure these irregularities can be measured using wavefront technology and correction of these irregularities incorporated into the LASIK treatment procedure. Wavefront technology measures the imperfections of the surface of the eye called 'higher order aberrations'. These irregularities of the cornea affect the quality of vision beyond the normal refractive errors of nearsightedness, farsightedness, and astigmatism. During a custom LASIK procedure the vision can be refined to provide better visual acuity than can be achieved with prescription glasses or contact lenses.
Custom LASIK procedures are either Wavefront Guided (WFG) or Wavefront Optimized (WFO). A wavefront is a map of the optical irregularities of the eye. A wavefront is unique to each eye measured, and because of this is often times compared to a fingerprint. A wavefront scan measures, maps and quantifies both the lower order aberrations (LOAs) and the higher order aberrations (HOAs). Low order aberrations are the aberrations that can be corrected with glasses or contact lenses, which is the amount of nearsightedness, farsightedness or astigmatism that an individual has. Conversely high order aberrations cannot be corrected with glasses or contact lenses. It is these high order aberrations that are responsible for night time glare and halos as well as contrast sensitivity.
Wavefront LASIK, which received FDA approval in 2002, currently offers the best possible vision correction. That's why, due to their demanding visual requirements, U.S. Navy and Air Force fighter pilots and NASA's Astronauts are only treated with wavefront technology.
In one government sponsored FDA clinical study, 93% of wavefront LASIK patients saw “20/20 or better”, and 76% saw better than 20/16.
In another FDA study, 98% of patients saw 20/20 or better
With wavefront technology, it is ten-times more likely to see better at night than with glasses or contacts
What is the difference between Wavefront Optimized (WFO) and Wavefront Guided (WFG) procedures?
Wavefront Optimized (WFO): The term “Wavefront Optimized' is highly confusing for consumers because it implies that these treatments are based on actual wavefront testing. Instead, as in conventional LASIK procedures, the patient's refraction alone is used to program the wavefront optimized laser treatment plan. Wavefront optimized (WFO) technology does not address pre-existing higher-order aberrations. Wavefront optimized technology is more effective than conventional LASIK in minimizing the induction of higher-order aberrations as a result of the LASIK procedure. The Wavefront Optimized treatment is not a true customized procedure, but rather applies precalculated aspheric treatment protocols to limit induced spherical aberration as a result of the LASIK procedure.
Wavefront Guided (WFG): In Wavefront Guided treatments both the low-order aberrations (nearsightedness, farsightedness and astigmatism) as well as the high-order aberrations are corrected. Wavefront Guided technology uses three-dimensional measurements of the cornea to create a customized profile. This is distinctly different from conventional LASIK and Wavefront Optimized LASIK treatments, in which the subjective refraction is used to program the treatment laser. In addition, Wavefront Guided treatments utilize iris registration to ensure that the treatment performed on the cornea is an exact match to the surgeon's intended treatment pattern. Wavefront Guided treatments also incorporate a pupil-tracking system, which compensate for cyclotorsion and pupil centroid shift, which maintains centration during treatment. Wavefront Guided treatments are used in LASIK procedures performed using Advanced CustomVue technology with the VISX STAR S4 laser.
What are Topography Driven Algorithms?
Topographically guided excimer laser treatments have become available in recent years, and used in LASIK procedures performed using Bausch and Lomb lasers. There are many challenges to developing a successful topographically driven excimer algorithm. The most challenging issue is the inherent inaccuracy in measuring corneal height data. These errors are significant and concerning when compared to wavefront measurements. The instruments used in corneal topography or tomography are at best accurate to a few microns. Errors are inherent in this measurement process and compounded moving from the corneal center to the corneal periphery. As a result, topography driven treatments produced errors in the 0.25 diopter range. In comparison, CustomVue wavefront measurements are accurate and reproducible at the sub-micron level with treatment errors in the hundredths of a diopter.
The Advanced CustomVue procedure has the broadest FDA-approved, custom wavefront-guided treatments available today for individuals with nearsightedness (myopia) and farsightedness (hyperopia) with or without astigmatism.
The Advanced CustomVue procedure consists of the following four steps:
Acquire: Wavefront error data is collected using the AMO WaveScan System
Design: A customized treatment is designed using the data collected on the unique characteristics of each eye using proprietary algorithms
Align: The treatment is aligned to the patient's eye using Iris Registration technology, which links diagnostic information to the treatment delivered during the Advanced CustomVue procedure
Deliver: Advanced CustomVue delivers an unprecedented level of precision and accuracy
Results – that's why more LASIK patients chose Advanced CustomVue by AMO using the VISX Star S4 laser than any other laser system available today.
Check out our other LASIK blogs:
- LASIK Screenings
- LASIK: Eliminating Glare & Halos
- LASIK over 40
- PRK versus LASIK
- Monovision LASIK
- Different Lasers
- Preparing for LASIK
- LASIK Recovery