Technology has dramatically changed over the past several years as new technologies have emerged. Motwani Lasik Institute is one of the very few centers using the most advanced laser in the country, and also one of the most advanced in the world, the Alcon Wavelight EX500. This machine builds on the very significant advances of its predecessor, the Allegretto 400, and the differences with other lasers is nothing short of dramatic.
The most common laser used in San Diego, and in the United states, is the Visx Star S4. The Visx Star S4 was originally introduced in 2003, only 7 years after laser vision correction was approved in the United States. It still uses essentially the same design as the original Visx which was engineered in the early 90’s. It added a more complicated tracker, the IR system in 2007, but the laser stayed the same. The broad beam technology in the Visx dates back to the early 1990s. 20 plus years in the world of eye laser technology, just like in computers, is a very long time ago indeed. The very first Wavelight laser was introduced in 2003. The first versions of this flying spot laser first came out when development of the Visx stalled. Since then, three generations of the Wavelight laser have been introduced, culminating in the EX500 which became available in 2013 in the United States. Wavelight is a German company, based in Erlangen, Germany, and now wholly owned by the American pharmaceutical company Alcon.
The EX500 is not only technically far superior to the Visx laser, it is also much more ergonomically designed for the surgeon helping them to be more efficient, less distracted, and safer. It represents, in our opinion, nothing less than a total re-think of an eye excimer laser.
Why don’t more laser centers have the EX500? The simple answer is cost. Advanced technology simply does not come cheaply. If a laser center and its surgeon are not fully dedicated to laser vision correction, it simply does not have the patient base to support such a machine.
|B&L Technolas* T217 Zyoptix||Nidek*|
|Visx Star* S4*||WaveLight® Eye-Q||Zeiss MEL 80*||WaveLight® EX500|
|Type||Scanning spot||Scanning slit||Variable broad beam||Scanning spot||Scanning spot||Scanning spot|
|Beam Size (mm)||1–2||2×9||0.65–6.5||0.95||0.7||0.95|
|Rep rate (Hz)||100||100||10–20||400||200||500|
|Avg fluence (mJ/cm2)||120||140||200||200||200||200|
|Eye track rate||100 Hz||200 Hz||60 Hz||400 Hz||50 Hz||1050 Hz|
The Need for Speed- the Wavelight EX500 is the fastest laser in the United States, and one of the fastest in the world.
In the world of laser eye re-shaping to get rid of myopia, hyperopia, and astigmatism speed equals accuracy. The reason why is simple: when you expose the bed of the cornea (the part of the cornea that needs to be-reshaped to get rid of your glasses), it starts to de-hydrate. Since the laser works on the water molecules in the corneal cells, the longer the laser takes the less accurate it becomes. In this world, seconds count, and count a lot! Studies have shown significant decreases in accuracy and increased need for a second procedure in slower lasers. And yes, you can also extrapolate that a slower surgeon may be a less accurate one! Obviously, less accuracy means a correction that isn’t as good and leads to more enhancements or second surgeries.
The Wavelight EX500 treats each diopter of nearsightedness (myopia) in 1.4 seconds, making it one of the fastest lasers in the world. In comparison, the VISX Star S4 IR (the latest VISX laser) takes 5 seconds to treat every myopic diopter. That means a -5.00 diopter treatment takes only 7 seconds with the EX500, but takes 25 seconds with the VISX! With a -10.00 D correction, the EX500 takes 14 seconds, and the VISX takes 50 seconds!
The speed differences become even more dramatic when treating hyperopia (farsightedness). Each diopter of hyperopic correction on the Wavelight EX500 takes 3.75 seconds, but on the VISX Star S4 IR takes 20 seconds! That means a +3.00 takes 11.25 seconds on the EX500, but takes 60 seconds on the VISX. A +6.00 diopter correction (which the EX500 is FDA approved for, and Dr. Motwani has performed many times) takes 22.5 seconds on the EX500, but takes an whopping 120 seconds on the VISX, essentially making higher hyperopia procedures technically undoable on a VISX. This has been reflected in the unwillingness of VISX surgeons to even do these cases, thereby telling people they are not candidates when in reality on a different laser they are.
The VISX’s speed problem is exacerbated by the its Iris Registration eye tracking system as that can take precious time to set up and track an eye, thereby allowing the cornea to dehydrate further. The tracking capture of the EX500 is very rapid, virtually instantaneous.
Eye Tracking to Follow Eye Movements
The EX500 tracks eye movements at 1050Hz, and guides and moves the laser to follow eye movements to ensure that the laser re-shaping occurs exactly where it is supposed to, and that the laser pattern is very precise. That means the EX500 tracks your eye 1050 times a second, twice as fast as the 500 times a second that the laser is working to remove tissue.
In comparison, the VISX Star S4 IR with Iris Registration has a tracker that only works at 60 Hz, or tracks the eye 60 times a second. This much slower tracker has a much harder time keeping up with rapid eye movements.
The EX500’s tracker is able to compensate for eye lateral movements, pupil centroid shift, and also cyclotorsion or eye rotation. It can track very large pupils, up to 8mm wide, and has a latency time of only 2 milliseconds.
The EX500 Is The Only Laser In The United States That Can Measure the Thickness of the Cornea During the LASIK Procedure.
Measurement of corneal thickness is important, because it tells a surgeon how much tissue a patient has, and therefore how much can be removed safely. Too much tissue is a bad thing as it can lead to loss structural integrity in the cornea and to irregular astigmatism.
The EX500 is the first and only laser in the U.S. to be able to measure the corneal thickness using a non-contact light based measuring device while the patient is under the laser. That means that the surgeon can measure the thickness of the cornea before and after the LASIK flap, and knows exactly how much tissue is present, how thick the flap is, know exactly how much can be removed, and how much has been removed. This increases the safety of laser procedures, whether they be LASIK, PRK, EPI-LASIK, or LASEK.
The Best “Better than 20/20” Results
The predecessor to the EX500, 400Hz system had the best better than 20/20 results. In FDA studies, it had a 75.9% 20/16 rate using the Wavefront Optimized ablation pattern for myopic corrections. It’s expected that the EX500, as an evolution of the 400, will be at least as good if not better in these results.
Patient Comfort and Limiting Stress of Procedure
Getting laser eye surgery can be a stressful experience, not because the procedure is physically difficult for the patient, but simply because having a procedure on your eyes can be stressful or even scary for some. The best way to make the process easier is to make it as stress-free, smooth, and as efficient as possible. A quick, efficient, but careful surgeon combined with a very fast laser decreases the amount of time the patient spends under the laser. This makes for a less stressful procedure for the patient, and it also decreases the amount of time the eye is being worked on, thereby decreasing the stress to the eye tissues. Under the laser, the time difference between 7 or 8 seconds and 22 seconds seems much longer, not to mention the time difference for hyperopes might be 14 seconds and 80 seconds! This decreased stress to the tissues results in faster recovery times, and people start seeing faster with faster healing times.
This laser is so fast that eyesight can be corrected faster than it takes to put in your contact lenses!