Wavefront Technology and Custom Vue Wavefront guided Ablation

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How the CustomVue PRK and LASIK Procedure Works

To correct myopia, the cornea needs to be flatter, so the laser removes more tissue from the center than the edge. When there is astigmatism, the eye is flatter more along one axis (e.g., horizontal) than in the other (e.g., vertical). The excimer laser can only remove corneal tissue to correct astigmatism; the cornea needs to be made stepper in the flatter meridian, so the laser removes more tissue from the flatter meridian than the steeper meridian. The eye surgeon creates a unique treatment plan from the WaveScan System to guide the laser. The laser removes tissue from the eye according to treatment plan (algorithm) utilizing the variable spot scanning.

The above example represents the wavefront from
a myopic (nearsighted) and astigmatic eye (-2.25-1.25x11).

Conclusion

I hope that this has provided you with a better understanding of the new and exciting wavefront technology. You must always keep in mind that all though we can now identify and measure visual imperfections in your eyes 25 times more precisely than with standard methods used for contacts, glasses and conventional LASIK or PRK, and that we have a laser that can remove a very precise volume of tissue, we are dealing with a somewhat unpredictable healing responds of the cornea. However with CustomVue, a new standard in laser vision correction is established, providing a precise level of measurement and correction never before possible. Now people undergoing the new procedure (CustomVue) are experiencing less problems with night vision and a greater number of people are achieving 20/20. The procedure has become safer and more efficacious. After all, just like a fingerprint, each person's visual imperfections (optical aberrations) are 100% unique to each of their eyes.

Comparison of three laser platforms that are currently approved for custom treatments and clearing up common misconceptions

Currently there seems to be some confusion among potential patients who've been reading about wavefront refractive surgery on the internet for months and perhaps some ophthalmologists as to what the FDA approvals state for the correction of higher order aberrations by all commercially available custom treatments by the Excimer lasers for LASIK. A review of the relevant documentation will find the FDA approvals do not include language that supports the contention that wavefront-guided excimer lasers are FDA approved to correct higher order aberrations (HOA). Even though the data demonstrates more improvement in HOA after custom LASIK compared to conventional LASIK the FDA did not allow for labeling that states that it corrects higher order aberration. The language that is included in the FDA labeling states, that in the clinical study the average HOA did not decrease compared to pre-op. The labeling states that the amount of post-op HOA for custom LASIK was less compared to conventional LASIK.

ALCON RESULTS

Number of eyes 50.

Data submitted to the FDA

What the data shows for Custom LASIK done on the ALCON laser 38% of the eyes treated show an improvement in HOA, 42% show no change in HOA and 20% show an increase in HOA (compared to pre-op). In contrast to conventional LASIK done on the ALCON laser approximately 14% showed an improvement in HOA, 8% show no change in HOA and 82% show an increase in HOA (compared to pre-op).

B&L RESULTS

Number of eyes 80.

Data submitted to the FDA

What the data shows for Custom LASIK done on the B&L laser 37.5% of the eyes treated show an improvement in HOA, 50.9% show no change in HOA and 13.4% show an increase in HOA (compared to pre-op). In contrast to conventional LASIK done on the B&L laser approximately 12.8 % showed an improvement in HOA, 41.9% show no change in HOA and 45.3% show an increase in HOA (compared to pre-op).

VISX RESULTS

Number of eyes 351.

No data submitted to the FDA

What the data shows (company data) for Custom LASIK done on the VISX laser 25% of the eyes treated show an improvement in HOA, 45% show no change in HOA and 30% show an increase in HOA (compared to pre-op).

You can see from the data above that the amount of post op HOA was less for custom treatments than for conventional. Data on VISX conventional LASIK not available.

% People with a decrease (improvement), no change and increase in HOA compared to pre op for all three laser platforms. (Data from FDA study on the Alcon and B&L. Company data on the VISX )

What all the wavefront laser platforms clearly do is to induce less HOA than conventional LASIK. This translates in to better visual results in contrast gained post operatively in light and dark conditions (see the following 2 histograms below) and post-op visual acuity (see last histogram).

% Of people with contrast gain or loss in day time and night time compared to pre-op (FDA data on the Alcon and B&L. Company data on the VISX)

Contrast sensitivity (6 months) % significant* gain compared to pre-op. (Data from NAVY study complements of Dr. Shelhorn) *>0.3 (2 levels) at 2 or more spatial frequencies

Post-op uncorrected visual acuity comparing all laser platforms for LASIK

The question can be asked why does custom treatments result in better visual outcomes. The answer is three fold. First, computerized outcomes analysis is being utilized by all of the investigators involved in the FDA trials. This means that data on the outcome of all the previous patients are entered into the computer program and a nomogram adjustment or a physician offset is applied to the laser computer for the next eye to be treated. Another way of looking at it is that you are benefiting from all the previous patients the have been treated. We have been doing this at Grendahl eye associates since 1999. Second, in the computer generated treatment algorithms in the computer of the Wavescan are commands to place more pulses of energy out into the peripheral part of the cornea being treated. This results in less induced 4th order spherical aberration. Third is the new STAR S4 IR with auto centering, a three dimensional eye tracker and variable spot scanning.

4th order spherical aberration one of many HOA

Note that all the studies were done with LASIK and not PRK. WE think that custom PRK will be even better but no data is available from the FDA yet. At this time custom PRK is considered off label and we have been doing Custom PRK since July of 2003 with excellent results. Other individual physicians have been doing clinical trials with excellent results. I hope that this has provided you with a better understanding of the new and exciting wavefront technology and clear up one of the more common misconception regarding custom treatments.