Wavefront seeks a higher order of vision correction

By Sean Henahan

ORLANDO, FL - Customised ablation based on wavefront sensing not only offers immense potential for visual results of 20/20 or better but may also reawaken flagging consumer interest in refractive surgery.

Wavefront sensing initially helped open surgeons' eyes to the visual effects of a host of visual aberrations beyond cylinder and sphere, including spherical aberration, coma and trefoil.

With increasing clinical experience, treatment algorithms have been developed that enable surgeons to plan and implement the treatment of these 'higher order' aberrations, according to surgeons speaking at this year's annual meeting of the American Academy of Ophthalmology.

The algorithms seem to be working. Wavefront-guided ablation is beginning to live up to its promise of 'super vision', with the latest batch of clinical studies providing impressive results that go well beyond those provided by spectacle correction, contact lenses, presbyopic IOLs or basic LASIK procedures.

In addition to improved visual acuity, the customised procedures appear to be producing less glare and night vision complaints and better contrast sensitivity results.
One of the first things researchers noticed when they started performing wavefront analysis was that a fair number of patients who underwent regular LASIK ended up with increased amounts of higher order aberrations, particularly spherical aberrations.

Since that time, the overall safety of refractive laser procedures has improved as surgeons have learned how to better select patients and prevent the creation of such errors.
"Current clinical data is telling us that wavefront is increasing the safety of refractive surgery and improving the results. It is providing patients with better quality of vision than ever.

"At the same time, wavefront also gives us a tool with which we can retreat patients with visual problems that resulted from previous procedures," Manus Kraff MD explained at the conclusion of an all-day marathon session on wavefront technology.

Current clinical experience is beginning to translate into FDA recognition. During this year's conference, Alcon Laboratories announced that it had gained FDA approval for its LADARVision® system for wavefront-guided custom ablation, affording it the distinction of being the first in the US to gain such an approval.
Both Bausch and Lomb (Zyoptix) and Visx (Waveprint) have completed clinical trials and expect similar FDA approval within months.

In the Alcon FDA trials, 98.6% of eyes treated for myopia achieved uncorrected visual acuity of 20/40 or better, with 79.9% reaching 20/20 or better.
Improvements were also seen in contrast sensitivity, which is associated with higher order aberrations. The FDA approved the system for the correction of myopia within the range of 0.0 D to -7.0 D with up to 0.5 D of cylinder.

The latest results for the Visx Star S3 excimer laser and WaveScan system are also impressive. Nearly all patients followed for six months in a multicentre US study had uncorrected visual acuity of 20/20, with 73% seeing 20/16 or better.
The Zyoptix system from Bausch & Lomb is also producing some remarkable results. In a study of 340 myopic eyes, 91.5% had uncorrected visual acuity of 20/20 or better, with nearly 70% achieving uncorrected acuity of 20/16 or better.

"It is remarkable. Wavefront is doing more than produce reductions in induced aberrations. It is giving patients better uncorrected vision than they have ever had, even with correction," Stephen Slade MD, FACS said.
Wavefront systems have been available in Europe for more than a year. As a result, European surgeons have a head start on the Americans in terms of clinical experience with wavefront-guided ablation.

This 'real world' experience gives an idea of how wavefront may be applied in different ways in daily practice.

"We are much more independent in Europe in the use of this technology. We are learning that wavefront ablation in LASIK does improve results but may not be necessary in all patients. Rather, we find that wavefront is useful in determining who might benefit.

"We are not routinely using customised ablation in patients with a low amount of aberration but do find it beneficial in patients with higher order aberrations," Lucio Buratto MD said.

At the Vardinoyannion Eye Institute of Crete, Sophia Panagopoulou PhD says surgeons now use wavefront to screen all patients, gleaning much useful information on higher myopes and higher order aberrations.
"The best achievement so far has been the ability to reduce induced aberrations. In the future, as the technology improves, I expect we will use the technology to plan an ablation based on the patient's specific needs," she remarked.

The promising results with wavefront-guided LASIK come at a time of economic turmoil around the world. This is reflected in a significant drop in demand for LASIK procedures in major markets over the past 12 months or more.

For example, the demand in the US has plummeted in direct proportion to the consumer confidence index, a fact which is apparent in current stock prices on the low end for laser makers.

"The economy is certainly an issue. But I think something else that is happening is that potential patients are worried about the idea of undergoing a procedure that may worsen their vision in some way.

"In this respect, the latest wavefront data is very positive since it indicates that not only does the procedure not induce problems, it provides significant visual improvement. I think once the word gets out on the safety of this procedure, the patients will begin to come in increased numbers," Karl Stonecipher MD said.

While patients may be hesitant, interest among surgeons appears to be growing. The latest ASCRS/ESCRS refractive survey of US and European surgeons' practice habits shows a significant growth in interest in wavefront-guided ablation from just one year before.

The survey indicated that in 2001 10% of surgeons were performing wavefront-guided ablations, up from only 2.5% in 2000.

Putting aside the competing claims of different manufacturers, the rapid development of wavefront science has been a tremendous boon to the field of refractive surgery, Stephen Trokel MD said.

"There is no doubt that wavefront technology has made a lot of things better. It has led to improvements by all companies in the field in many areas, such as in treatment algorithms and eye tracking technology.

"Wavefront is providing solutions to problems where we simply had no solutions to offer before," he added.

Many speakers noted that wavefront applications are still in the early stages. There is still much to learn about the theory and practice of the technology, especially about the nature of higher order aberrations and the role they play in visual acuity.
There is also considerable debate about the place of corneal topography in customised ablation.

Moreover, while current studies have focused on myopia and astigmatism, clinical studies are also well underway exploring the role of wavefront analysis in the management of both hyperopia and presbyopia.

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