KnowLASIK

One of the most popular LASIK excimer laser systems in use around the world is the AMO VISX Star S4 with Wavescan wavefront custom LASIK. This is currently the most popular LASIK system in the USA and the most popular LASIK system in the San Francisco, San Jose, San Diego, Los Angeles, New York, and New Jersey. While LASIK patients all around the world use the AMO VISX excimer laser, it is most popular in the USA. Outside the USA, Bausch and Lomb, Nidek, Zeiss, and other excimer laser manufacturing companies have a much greater market presence.

The VISX Star S4 is typical of most LASIK systems in that it uses a 193 nm wavelength laser to treat the cornea and reshape it to the desired refractive correction needed for good vision. VISX Star S4 is an excimer laser that is FDA approved for wavefront treatment of myopic (near-sighted) prescriptions of up to -11.00 D with astigmatism of up to -3.00 D and for hyperopic (far-sighted) prescriptions of up to +3.00 D with up to +2.00 D of astigmatism.

The AMO VISX STAR S4 platform is categorized as a variable spot scanning excimer laser with a beam that varies in size from 0.65 mm up to 6.5 mm over the treatment area. The variable size of the beam allows for shorter treatment times and more conservation of tissue. The VISX STAR S4 also boasts a variable repetition rate to allow for optimization of treatment times.

A standard LASIK prescription is generally treated in about 30 seconds. The rapid treatment time by the VISX Star S4 excimer laser platform improves treatment results by allowing the LASIK surgeon to have less time where the flap is open or less time during mid-treatment.

Similar to other LASIK systems, the VISX Star S4 has an active eye tracking system, known as the ActiveTrak 3-D Active Eye Tracking System. This eye tracking system is marketed as capturing all 3 dimensions of intra-operative eye movements with no dilation required. The VISX Star S4 also utilizes ActiveTrak Automatic Centering. This capability locates and then automatically sets the treatment center to the center of the pupil.

Most impressive of the VISX Star S4 LASIK system is the Iris Registration (IR) capability that it has available. There are many measurements of the optics of the eye that are particularly sensitive to orientation of the eye during surgery. Astigmatism, trefoil, coma, and other higher order aberrations require an accurate alignment with the original measurements taken in order to provide an accurate treatment. The eye is known to slightly rotate once the patient has changed from a vertical sitting position (where the measurements were taken) to a horizontal position (where the surgery is performed). This eye rotation was not adequately adapted for prior to the VISX iris registration.

The VISX Star S4 is the first Iris registration system available and the first FDA approved, fully automated, non-contact method of alignment of the correct CustomVue treatment to the corneal site. In the San Francisco Bay Area there are a limited number of LASIK clinics that provide iris registration. This upgrade is extremely important as it provides a solid means of providing the most accurate treatment available.

The VISX Star S4 CustomVue procedure tailors a distinct correction for each individual – in fact each treatment is “designed” by the unique characteristics of the individuals’ eyes. WaveScan technology captures unique imperfections in each individual’s vision that could not have been measured before. This new level of measurement provides 25-times more precision than measurements using standard methods for glasses and contact lenses. WaveScan technology produces a detailed map of the eye – much like a fingerprint, no two are alike and translates this information into a set of CustomVue treatment instructions for the laser. WaveScan transfers these digital treatment instructions to the laser, providing a new level of precision and accuracy.

FDA Clinical Study Results

VISX’s FDA clinical study results were remarkable. Among other things:

• At one year after the VISX CustomVue procedure;
• 100% of the clinical study participants could pass a driving test without glasses or contacts
• 98% of the clinical study participants could see 20/20 or better without glasses or contacts
• 70% of the clinical study participants could see 20/16 or better without glasses or contacts

Four times as many clinical study participants were very satisfied with their night vision after the VISX CustomVue procedure, compared to their night vision before with glasses or contacts.

For patients in San Francisco, San Jose, Los Angeles, New York, New Jersey, and San Diego, the AMO VISX Star S4 provides an advanced laser platform that offers accuracy and reliability.

What the marketing of the FDA clinical study doesn’t report

While the VISX Star S4 is an excellent excimer laser platform, the FDA clinical study was carefully designed by VISX in order to provide the desired results. While the results initially seem superior to other excimer lasers (such as Bausch and Lomb, Alcon, and other companies) here are some facts to consider.

1. Patients were carefully selected. All patients chosen initially had 20/16 vision when using the customvue wavefront prevue lens. This means that the LASIK patients were initially seeing even better than 20/20. This means that patients seeing 20/20 following LASIK would in fact be seeing 1 line worse than they had with glasses prior to surgery.
2. FDA Clinical study patients had low prescriptions. The VISX LASIK patients in the FDA clinical study average only 3 diopters of myopia. This is much lower than any other FDA clinical study, including Alcon, Bausch and Lomb, Nidek, and Alegretto.
3. Patients had higher amounts of higher order aberrations following custom LASIK than they did before custom LASIK. VISX had previously been labeled as causing night problems and night glare with the VISX Star S3. The marketing for the VISX Star S4 wanted to avoid this label. While the study tries to report a high amount of satisfaction for night vision the results have been carefully selected. The VISX Star S4 is certainly an improvement over the VISX Star S3 but LASIK can still cause night vision difficulties, particularly for patients with large pupils or high prescriptions.
4. “Customvue is 25 times more accurate than conventional LASIK.” While custom LASIK is an improvement over conventional LASIK the reported value of 25 times is not accurate. The customvue LASIK technology takes measurements in 0.01 increments. Previous measurements using a phoropter used 0.25 increments. VISX wants to advertise 25 times more accuracy but unfortunately reporting in 0.01 increments does not reflect that same level of accuracy. Customvue measurements can vary as much as 0.50 or more between measurements. In order to report 0.01 degree accuracy, measurements would have to vary on the order of 0.01.

Overall the VISX Customvue Star S4 is an excellent laser in the hands of a skilled and experienced LASIK surgeon. Patients should feel very comfortable with this laser if the LASIK surgeon has sufficient experience. This excimer laser is particularly effective because of its wavefront and its iris registration capabilities.