Time for a Change to the All Laser-LASIK Approach

Flap/Flap/Zap/Zap vs. Flap/Zap/Flap/Zap

BY LOUIS PROBST, M.D.

In the relatively short history of LASIK, there was a time when performing a same-day, bilateral treatment was exceptionally controversial. Today, it's only in extraordinary circumstances that we don't treat both eyes in the same surgery session. Bilateral LASIK has become accepted because the conventional wisdom is that if you do the entire procedure in one eye and it's successful, then it's reasonable to proceed with the other eye.

As part of bilateral LASIK, the standard approach is to cut the flap with a microkeratome, lift the flap, perform the ablation, replace the flap and then perform the fellow eye. Yet, when surgeons started to use the femtosecond laser for flap creation, the vast majority switched to an approach that created both flaps first, followed by laser ablation — the theory being that this was a more efficient way to do bilateral intraLASIK. As it turns out, it's not. After conducting a time comparison study on my own patients, I've come to the conclusion that the approach we've long used with mechanical microkeratomes is by far the most efficient LASIK procedure possible.

Flap/Flap/Zap/Zap vs. Flap/Zap/Flap/Zap

Intuitively, it seems simpler to cut both flaps first with the femtosecond laser and then do the excimer laser ablation because you are using two different lasers. It seems like more work to shift the patient between the two lasers more than once. To find an answer, we conducted a clinical study that looked at the time differences between two approaches: flap/flap/zap/zap and flap/zap/flap/zap.

The study involved two randomized groups of five patients (20 eyes). All flaps were created with a 60 kHz femtosecond laser (Advanced Medical Optics [AMO]/IntraLase, Santa Ana, Calif.) and all excimer laser ablations were done with the AMO/Visx Star S4 CustomVue excimer laser system (AMO/Visx, Santa Clara, Calif.).

In one group, I performed my typical bilateral procedure — cutting the flap in the right eye, followed by excimer laser ablation and then repeating the process for the left eye. In the second group, I cut flaps in both eyes, followed by flap-lifting and excimer laser ablation. We timed the procedures to see how the times compared.

In the flap/flap/zap/zap group, the average procedure time was 8.23 minutes, 31 seconds. In the flap/zap/flap/zap group, the average procedure time was 7.46 minutes, 29 seconds. While there is not a massive difference between the two approaches, it is clear that the second approach actually takes less time when you are performing intraLASIK.

So why is there a perception that it is the other way around? Much of it has to do with the idea of physically moving the patient between the two laser beds in order to do the two steps because there is a height difference between the lasers. In reality, a simple adjustment makes it possible to keep the patient on the excimer laser bed — if you are using either the AMO/Visx or the Bausch & Lomb Zyoptix lasers.

Bed Adjustment

The original intention with the IntraLase femtosecond laser was that it would be the same height as the Visx laser, the most commonly used excimer laser platform in the United States. However, the manufacturer quickly discovered that the femtosecond laser needed to have rubber padding underneath its footings to absorb any shocks coming from the floor. This raised the IntraLase about one inch, making it less convenient to rotate the excimer laser bed between the two lasers without making adjustments.

What I determined was that if you raise the bed on either the Visx or the B&L laser by one to two inches, you can get the patient in a perfect plane for both, allowing you to move the bed between the two lasers with no additional adjustments.

The Opaque Bubble Layer

An additional reason given for the flaps first, then ablate approach cited by some surgeons was the need to let the opaque bubble layer (OBL) dissipate before proceeding with the excimer ablation. With the 15 and 30 kHz femtosecond lasers, you need to wait 10 to 15 minutes to allow for absorption of the OBL. Now, with the 60 kHz model, OBL is rare and if it does occur, it's fine and so superficial that a WeckCel sponge can be used to wipe it away. This means there is no need to wait for the OBL to clear before moving onto the excimer ablation.

Better for the Patient

There is an additional reason that I use this approach — I believe it is better for the patient and enhances the entire surgical experience. I want to be able to completely treat one eye, know that the procedure went well and then move on to the second eye with that knowledge in my head, as well as the patient's. I have found that it is very comforting to the patient to know that the first eye went well and that there were no complications. A key point in my patient interaction is to say, after I've treated the right eye, that the procedure went perfectly, the flap looks good and that he or she did a great job keeping their eyes steady during the excimer laser ablation. I then ask the patient if it is okay for me to proceed with the left eye. It's a subtle thing, but it puts the patient back into a decision-making role.

Iris Registration

The final reason that I prefer the flap/zap approach is because the dominant treatment I use is the AMO/Visx CustomVue wavefront treatment with iris registration. The iris registration on this system works very well — particularly on virgin eyes and PRK. It also works fairly well in LASIK cases. I found it more difficult to get the iris registration to work with the femtosecond laser until I played around with the sequence of each treatment.

In all cases, I now start with the patient underneath the Visx laser where I place the speculum and do the iris registration capture. I then move the bed and position the patient underneath the femtosecond laser to create the flap and then back to the excimer laser. This sequence works extremely well, with iris capture in 99% of eyes, and allows me to offer my patients the best possible procedure with the femtosecond laser, iris registration and a wavefront-guided treatment.

When I first conducted this study, and presented it at a number of meetings, quite a few surgeons expressed resistance to the concept. What I tell them is this — ultimately, what we want is to offer the absolute best for our patients, while at the same time performing a procedure that is efficient and user-friendly. In this approach with intraLASIK, I believe we are able to achieve that goal. OM

As a medical director for TLC Vision, Dr. Probst has performed over 80,000 LASIK procedures. He has published more than 50 articles in peer-reviewed journals, as well as written 70 book chapters on refractive surgery. Dr. Probst has authored six reference textbooks on LASIK including The Art of LASIK, which is used by refractive surgeons and eyecare professionals worldwide. As a leader in refractive surgery, Dr. Probst has developed 10 instruments specifically designed for LASIK.