Richard A. Levinson, M.D. > WaveLight EX500 Allegretto and VISX Star S4 CustomVue Excimer Lasers. Which is “better”?

WaveLight EX500 Allegretto and VISX Star S4 CustomVue Excimer Lasers. Which is “better”?

Colorado Custom LASIK and PRK, Laser Vision Correction Eye Surgery, with  the WaveLight EX500 and VISX Star S4 CustomVue Wavefront LASIK Technology in the Denver & Boulder Metro Area

Laser Vision Correction is performed with an Excimer Laser. The Laser energy reshapes your cornea, effectively shaping your glasses prescription permanently on the surface of your cornea. I want to explain the similarities and differences between the two primary Excimer Lasers systems that are available to you, the WaveLight EX500 Allegretto and the VISX Star S4 CustomVue.  I have extensive experience with both of these Excimer Laser. They are both state-of-the-art, excellent pieces of equipment, but like any technology, they each have advantages and limitations. Both Lasers use the same argon-fluoride Excimer Laser technology to reshape the cornea of your eye. The primary difference between the two Excimer Lasers is that the VISX CustomVue is more precise in mathematically modelling and mapping the shape of the cornea and the WaveLight EX500 Excimer Laser has a much faster treatment time. The VISX CustomVue Wavefront Analyzer identifies “higher-order aberrations” (surface irregularities) unique to your specific eye. However, most of these higher-order aberrations are of the 1-2 micron size range – about the size of a small virus particle.  Realistically, irregularities of this size are probably too small to be treated accurately by any present-day Excimer technology. The WaveLight EX500 reshapes the cornea approximately 8 times faster than this VISX Star S4.  The longer the treatment time, the more susceptible the cornea is to dehydrating. Dehydration significantly effects the precision of the Excimer Laser treatment, especially with the VISX Star S4 because of its slower firing rate.  Both Excimer Lasers use wavefront technology, but apply the technology differently. The VISX is Wavefront-Guided and the WaveLight is Wavefront-Optimized. The VISX Wavefront-Guided technology is more precise than the WaveLight Wavefront-Optimized technology in mathematically modeling and treating your eye in LASIK and PRK but is probably not any more accurate because of  the limitations of the ability of the Excimer Laser to actually treat these micron-size irregularities. Basically, in my experience, both Laser Systems are excellent but the advantage of the 8 times faster treatment with the WaveLight is more clinically important than the theoretically more precise mathematical modelling and astigmatism mapping (see below) of the VISX Star S4.

Wavefront technology was initially designed to identify and correct microscopic aberrations in the complex adaptive-optic telescopic systems used in astrophysics (astronomy). By using a scanning laser, an optical system can be analyzed with accuracy never before possible. And by identifying subtle irregularities in complex optical systems, such as telescopes or your eye, microscopic adjustments can then be made in the optical system, allowing significant, previously unattainable improvements in the quality of the optical system. This technology has been adapted for analyzing the human eye, specifically for use in Laser Vision Correction.

VISX Wavefront-Guided technology allows me to customize your LASIK treatment specifically for your eyes. The VISX CustomVue-Analyzer measures your eyes and generates a specific, unique wavefront map of your eye. Although millions of eyes may have the same refraction (glasses prescription), no two eyes will have the same wavefront pattern. Your unique wavefront pattern is programmed into the VISX Star S4 Excimer Laser, allowing customized LASIK treatment specific to your eye, increasing the precision and accuracy of LASIK. The WaveLight Wavefront-Optimized system does not have a Wavefront-Analyzer to do a wavefront mapping of your eye to customize your treatment specifically for your eye. The WaveLight treatment profile was designed based on wavefront measurements from a large sampling of corneas. This pooled data was then incorporated into the design of the WaveLight treatment profile. This approach uses pooled wavefront data to modify and “optimize” the treatment profile, but it is not customized specifically for your eye. The WaveLight Wavefront-Optimized system is designed to treat one type of higher-order aberration, spherical aberration, by creating a “prolate pattern”. However, the WaveLight does not treat other higher-order aberrations (coma, trefoil). VISX CustomVue identifies and treats all of these higher-order aberrations.

The VISX Wavefront-Guided system more precisely mathematically models your eye. The VISX CustomVue Wavefront Analyzer generates a computerized, 3-dimensional measurement of your eye. (We take a “picture” of your eye. You don’t feel anything.) These wavefront measurements are more precise than any other measurement system and can treat corneal imperfections that glasses or contacts cannot correct

Additionally, the VISX wavefront technology also includes “iris registration”, which accurately determines the rotational orientation of the Laser Treatment for correcting your astigmatism. No other FDA Excimer Laser has this technology. Other Lasers have “auto-trackers” that orient the Laser in the x,y and z directions (i.e. left, right and up/down) but the VISX auto-tracking system with iris-registration also determines precise rotational (clockwise/counterclockwise) orientation. Iris registration, which is only available on the VISX Laser system, provides a significantly increased precision for treating your astigmatism.

FDA studies on patients who had LASIK on the VISX Star S4 CustomVue Wavefront system showed:

  • 96% of patients in the FDA Study were satisfied with their vision AFTER CustomVue LASIK while only 78% were satisfied with their overall vision BEFORE CustomVue LASIK.
  • 2/3 of study patients saw better at one year after CustomVue Wavefront LASIK than they did before surgery with their glasses or contacts.
  • At 1 year post-op after Visx CustomVue Wavefront LASIK, 99% of FDA study patients saw 20/20 or better, 75% of patients saw 20/16 or better AND 23% saw 20/12 or better!! 20/12 vision approaches the theoretical limit that the human eye is capable of seeing. We rarely attain 20/12, or even 20/15 vision with glasses or contacts!
  • Four times as many study patients were very satisfied with their night vision AFTER the CustomVue LASIK than were satisfied with their night vision BEFORE CustomVue LASIK.
  • 30% of patients complained of glare at night before CustomVue LASIK and only 8% complained of glare at night after CustomVue LASIK.

This VISX Wavefront-Guided system with Iris-Registration is  valuable in identifying and treating astigmatism and higher-order aberrations of your eye. The WaveLight system is an excellent Excimer Laser in treating lower-order aberrations (nearsightedness and farsightedness) but is not as theoretically as precise as the VISX in treating astigmatism. However, the WaveLight does have the significant advantage in that its treatment time is approximately 8 times faster than the VISX. I have found this to be a critical advantage for the WaveLight Excimer Laser.  Corneas quickly dehydrate while being lasered, especially in Colorado where the air tends to be dry.  With evaporation, the Excimer Laser tends to run “hotter” and can remove more tissue than expected, making the results less predictable.  The significantly faster treatment time of the WaveLight eliminates, or at least decreases, dryness concerns.  I have been primarily using the WaveLight Excimer Laser since October, 2015 and I have found the results to be slightly more predictable and precise than than the VISX Excimer Laser.

Patients with small pupils (under 5 mm), with over 6 diopters of nearsightedness, 3 diopters of astigmatism or with farsightedness cannot be treated with VISX Wavefront CustomVue.

Please call my vision correction office in Denver, Colorado if you have specific question or to arrange a complimentary (free) consultation to see if you are a candidate for Wavefront CustomVue LASIK or PRK.

Phone (303)393-0347
Fax (303)393-1026

Laser Vision Correction Surgeon Denver Boulder Colorado
Rose Medical Plaza, 4545 East Ninth Avenue, #270, Denver, CO 80220