Comparing Excimer Lasers - Does the type of laser make any difference?

In Chapter Eight I made the recommendation that one should choose a wavefront-guided excimer laser over a conventional excimer laser.  This argument is supported by some studies and not by others.  However, the wavefront-guided excimer lasers are also the latest generation lasers, which boast the most advanced laser algorithms (as outlined by Jack Holladay, M.D.).  The wavefront-guided lasers, therefore, tend to result in the smoothest post-op corneas and the lowest degrees of higher order aberrations (HOA’s) in vision, which translates into sharper vision with greater contrast sensitivity and less risk of halos, ghosting, and other night vision disturbances.

But, is one brand of laser better than another?  In order to answer this question and back up the answer with data, one needs patients’ eyes randomized to treatments with two or more different excimer lasers and prospective follow-up of results.  At this point in time, there is an extreme paucity of this type of study that compares the most modern of lasers across the board.  There certainly are a few studies that compare older generation lasers, however, I believe mention of these studies is a moot point when I have already advised that you should only have your procedure completed with the most advanced laser available.

A single study that compared custom LASIK, that is wavefront-guided (WFG) LASIK, utilizing two separate excimer laser systems is underway and has presented preliminary data.  In this study, Alcon’s CustomCornea and the Bausch and Lomb Zyoptix system’s results were compared[i].  In this study, fifteen patients (30 eyes) were treated with CustomCornea and 15 patients were treated with the Zyoptix system and patients have been followed up to one month.  All of the patients’ flaps were created with the Intralase femtosecond laser (IntraLASIK). 

At one month post-op, their report states, “the percentage of eyes with uncorrected visual acuity (UCVA) of 20/20 and 20/40 were similar with 93% and 100%, respectively, for CustomCornea eyes and 90% and 97%, respectively, for Zyoptix eyes.  A difference between the two groups is in the percentage of eyes with UCVA of 20/16, 20/12.5, and 20/10 with 80%, 47%, and 13%, respectively, for CustomCornea and 70%, 10%, and 0%, respectively, for Zyoptix. 

Obviously, both sets of results show extraordinary results, however, Alcon’s CustomCornea outperformed the Zyoptix system in this small study with short-term follow-up.  Longer-term follow-up may indeed change these early results, as post-op refractions can be unstable for at least several months following LASIK. 

A review of the literature reveals no other comparisons between the most advanced, wavefront-guided, excimer laser machines.  As such, I cannot make any other comparisons based on studies.  There certainly are theoretical and methodical differences between machines, but these differences may not necessarily translate into any definite differences in visual acuity outcomes.

Will You Have a Choice as to Which Excimer Laser is Used?

At the present time, the large majority of excimer laser procedures in the U.S. are being completed on VISX machines.  VISX presently dominates the U.S. market and most reports suggest that approximately 70% of excimer laser procedures are being completed with VISX machines.  Therefore, statistically speaking, you are most likely to have your excimer laser procedure on a VISX machine if you reside in the U.S.  There’s good reason for this:  VISX has an excellent track record and remains on the cutting-edge of technology with their machines and broad FDA approval to treat myopia, hyperopia, and astigmatism, especially with their wavefront-guided CustomVue Star S4 excimer laser system. 

If you intend to have your excimer laser procedure and a VISX machine will be used, I would strongly advise you to have your procedure completed with the CustomVue Star S4 excimer laser system, and if you have any significant astigmatism (greater than 0.5 Diopters), I would also advise that you shouldn’t hesitate to be sure their latest invention, Iris Registration, is also used.  This latter technology images the detail of the iris during the wavefront data-gathering phase of the procedure and then appropriately rotates the beam of the laser based on the rotational movement of the eye during the laser procedure itself.  Iris registration probably plays little role in the procedure in patients who have no significant astigmatism.

Likewise, with other excimer laser machines (and there are many excellent systems), I would strongly advise that you take it upon yourself to be certain your eye surgeon is using the latest technology because, as the studies have shown, it makes a difference in your outcome!  Don’t listen to any advice that suggests “it is all in how your surgeon uses the machine” and/or “it is the surgeon that makes all the difference”.  If that were true, why wouldn’t all refractive surgeons be using the Summit Apex excimer laser that was FDA approved in 1995, which has now been largely abandoned?  Well, for the same reason that you’re probably not viewing this on a 1990 vintage computer… they both keep improving!  Now trust me, I’m not denying that your surgeon is the most important element here.  He or she definitely is.  I’ll review that in more detail in Chapter Sixteen.  But, the best surgeons also tend to use the latest technology, which is partly how they stay on the forefront and get the best results. 

In the table below, I’ve listed all of the major excimer laser manufacturers and their latest technology machines.  When you visit your surgeon, if you find out he or she is using a system that antedates one of the systems below, please proceed with caution.  Ask questions.  Be certain that your queries are well addressed.