VISX - Wavefront and Beyond

SINCE its foundation in 1986, California-based Visx has become a leader in the field of excimer laser refractive surgery and a pioneer in wavefront technology.
However, the company is not resting on its laurels. While continuing to expand its refractive surgery horizons, the company's research and development efforts now also include areas that go well beyond its original vision.
In the refractive arena, Visx has built on the platform of the Visx Star 3TM excimer laser. That platform is a leader in US and Asian markets and is now making its presence known in Europe, particularly the UK.

The latest iteration of the Star 3 system includes the Wavescan wavefront diagnostic hardware and software package, the preoperative Prevue lens. The Wavescan upgrade is necessary to perform customised personal ablations.
The system also incorporates ActiveTrakTM, a 3D automated real-time eye tracking tool designed to optimise centration. On the development front, Visx is evaluating a new tracking system that uses iris pattern recognition software to detect cyclorotational eye movement.

The company is now focusing its efforts on encouraging surgeons to use the wavefront upgrade system not just for assessment, but to guide treatment.
The latest results from international clinical studies of wavefront-guided ablation using the Visx Star S3TM excimer laser and WaveScanTM system were presented recently at the annual XX Congress of the ESCRS in Nice. The results after three and six months are among the best so far reported anywhere for laser refractive surgery.

International protocols
In the US and international protocols, many patients ended up with postoperative uncorrected vision that was better than their best-corrected vision before surgery.
Almost 100% of patients who were followed for six months in a multicentre US study had uncorrected visual acuity of 20/20, with 73% seeing 20/16 or better.
Similar results were reported in an international study that included clinics in Europe, South America and Asia.

Interestingly, no nomograms were used in any of the studies. All procedures were performed using exactly the same set of algorithms developed by the company.
According to Carol Harner PhD, Vice-President of Research and Development at Visx, this reflects the company's long-term involvement with the Star 3 excimer system and associated software.
"We've been at this for a long time. With many years of clinical experience, we have learned how our laser interacts with tissue. We have a much better understanding of it now than in the early days.
"As a result we are much better at putting the algorithms together, so we get much better outcomes."

The Wavescan component of the system provides refraction and aberrometry data for assessment and outcome prediction.
In addition to regular sphere, cylinder, and axis, it produces an acuity map that provides all of the lower and higher order aberrations.
It can also produce a Bille aberration map looking only at the higher order aberrations. The system provides quantitative data on root mean square errors. The user can also look at point-spread function, Zernicke coefficients, Hartmann-Shack images, and difference maps.

Finally, the system produces a Waveprint, a colour-coded three-dimensional map of the patient's cornea that also helps the surgeon to assess the refraction and higher order aberrations and personalise the corrective procedure.
As surgeons have gained experience with the Wavescan system, Visx has initiated clinical trials that go beyond the original goal of planning primary procedures.
Studies now underway are evaluating the potential of wavefront analysis to correct patient complaints associated with primary LASIK, particularly problems with night vision.

In another presentation at the Nice ESCRS conference, Dr Julian Stevens, Consultant Ophthalmologist, Moorfields Eye Hospital, London, UK, presented his initial experience re-treating post-LASIK eyes with night vision complaints using wavefront guided ablation.
A majority of patients had quantitative and qualitative improvements in night vision symptoms following the re-treatment.

"We feel that we are now moving to a new level. We are now interested not only in making the good better but also in making the bad good," noted Dr Harner.
Another method for 'making the bad good' relies on topography rather than wavefront analysis. The Custom-Contoured ablation patterns, also known as C-CAP, recently received FDA approval for the treatment of decentred ablations.

The C-CAP package is a software upgrade to the Star 3 system designed to normalise the corneal curvature through unique ablation patterns. The system takes advantage of the diagnostic capabilities of the Humphrey Topographer and associated "VisionPro" Ablation Planning Software to analyse decentred corneal irregularities and identify appropriate treatment areas.

Clinical trials are also underway outside the US to evaluate the potential of the C-CAP system for treatment of post-LASIK irregular astigmatism.

Final frontier
Presbyopia has become the final frontier of refractive laser surgery. Following anecdotal reports of unexpected presbyopic symptom improvement in hyperopia treatment trials, Visx investigators conducted extensive topographic analyses of those patients.
This led to the development of several unusual ablation patterns now being evaluated in clinical trials. The new approach aims to steepen the central area of the cornea to provide a myopic region for near vision, while also targeting the peripheral optical zone targeted for emmetropia.

The WavePrint system is used to create the multifocal ablation profile for each patient.
Early trial results from Mexico and Canada indicate that the presbyopic multifocal LASIK strategy is safe, with no significant loss of best-corrected distance visual acuity.
While the data is very preliminary, the first reports indicate that patients are seeing improvements in both distance and near vision. The studies are ongoing in 14 centres around the world and the ablation profiles continue to be refined.
Looking to the future, Visx has partnered with 20/10 Perfect Vision, a research company in Heidelberg, Germany, to explore the potential of using real-time adaptive optics to guide ablation planning.

Wavefront deformations
The company has developed a prototype equipped with 40,000 individually movable micro-mirror facets to correct wavefront deformations.
The experimental device is designed to function with the Visx WaveScan diagnostic system. After obtaining a wavefront scan of the eye, the system employs the device to generate arbitrary surfaces for analysis.

The mirrors deform to provide a corrected wavefront with reduced aberrations. The patient then gets a video preview of what his corrected vision will be and the ablation parameters can be modified if necessary.
Macular degeneration might seem a long way from the company's roots in refractive surgery. Nonetheless, Visx has a multimillion dollar research project underway to develop innovative approaches to treating degenerative retinal diseases.

Taking advantage of its location in the Silicon Valley, the company has enlisted the aid both of Stanford University biologists and chip designers to develop innovative approaches to retinal diseases.
Working with the considerable scientific resources at Stanford, Visx is supporting a project to develop a bio-engineered film implanted with RPE-generating stem cells that would be transplanted into the retina.

The membrane would be inserted under the retina via pars plana vitrectomy to replace diseased areas of the RPE. That research is already in animal studies and human studies could begin as early as next year.
Another research project is underway that could someday help patients with more advanced macular degeneration. Researchers are developing an artificial retina that links neuronal cells and a digital camera using neurotransmitters to stimulate a visual response.

The Visx/Stanford research collaboration is also developing an artificial cornea. One objective is to make a plastic cornea replacement material that could be added to corneal tissue to enable refractive laser procedures to be done in otherwise unsuitable cases.

A related idea would be to use the same material topically. Surgeons would de-epithelialise the eye, put this material on, laser it and then the material would re-epithelialise. The entire procedure could be done without touching the actual corneal structure.
"These are long-term, well-funded projects. No company can do studies like these in-house. You need the type of attention and focus and interdisciplinary expertise that is available at Stanford.

"This enables researchers to draw on all of these resources, including tissue biology, growth factor biochemistry, silicon chips, lithography and polymer chemistry. This is a very powerful research programme," Dr Harner emphasised.
One notable hole in the Visx product line has been the microkeratome. Moving to fill the gap, the company partnered with AMO whose product list includes the Amadeus microkeratome but not a laser. The two companies now pursue co-marketing of the complementary technologies.

Visx is also pursuing research efforts in new microkeratome technologies. The company has partnered with Medjet Corp to provide support for that company's waterjet microkeratome.
The water-based system has many potential advantages, including smoother cuts with none of the metal fragments or chemical leftovers known to be associated with metal microkeratomes.

Visx has an option to buy Medjet Corp for $8 million. Dr Harner said the decision whether to take the option would be made following clinical work with the product now underway.
Like most other vision care companies, Visx is being buffeted by the economic uncertainty around the world.
Reflecting the reduced demand for LASIK procedures in the US, sales revenue was down 20% in the third quarter compared to the same period a year ago. Visx stock (traded as EYE on NASDAQ) recently traded below $8, down from a 52-week high of $18.15.

"Our year over year revenue comparisons reflect the difficult economic environment characterised by declining consumer confidence. However, there are positive underlying elements.

"Most importantly, sales of our WaveScan WaveFrontTM analyser are strong in anticipation of the US launch of custom LASIK procedures and more than 80% of our US customers have upgraded to the custom VISX STAR laser system," said Liz Davila, President and CEO of Visx, during a teleconference announcing third quarter 2002 earnings.

Ms Davila said the company expects revenue to pick up with the growing popularity of customised LASIK, along with a stronger US economy.
The company hopes to gain FDA approval for Wavescan guided ablations in the first half of 2003.

"Internationally, we have now launched custom LASIK and have already recorded our first per procedure fees for custom treatments performed in the international market.
"With an estimated 55 to 60 million candidates in the US alone that could benefit from laser correction surgery, we are optimistic about the long-term prospects of our business," she added.

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