Today, approximately one-third of my refractive surgery practice is surface ablation. I routinely choose this procedure for patients with thin corneas, for those with tear dysfunction (common in individuals over the age of 40), and for the many patients I see who have a safety-first mindset. I also think that the corneal surface may be the ideal location for highly refined customized laser ablations.
Until recently, my surface ablation procedure of choice was PRK. I had tried LASEK but found that it resulted in pain levels similar to PRK, with slower visual recovery. Although LASEK eliminated my concerns about haze, I did not find the procedure to be better than PRK. The buzz about LASEK, however, did focus attention on creating a viable epithelial flap, a process that led to the development of Epi-LASIK.
Epi-LASIK with the Moria Epi-K epithelial separator (Moria, Antony, France) is replacing PRK in my practice. The procedure may offer faster visual recovery and certainly less pain than PRK. The big question for many surgeons will be whether these improvements allow it to compete with LASIK.
As one of the surgeons participating in a Moria-funded, Institutional Review Board study of the Epi-K, I treated 39 eyes of 22 patients. Because we were asked to examine the patients on each of the first 4 days postoperatively, I specifically chose individuals with high cylinder or higher-order aberration for whom I felt wavefront-guided surgery was a must.
My learning curve for the Epi-K was short. I became comfortable using the instrument and the foot pedal within five cases. Most surgeons, I think, will be comfortable handling the epithelial flap after 25 cases. In my first 14 eyes, I overmanipulated the flaps and used too much BSS and anesthetic, both of which devitalize epithelial cells. When I changed my technique, as I will describe later, I achieved much better results. The data presented here are for the cohort of 25 eyes treated after I learned the lesson that less is more.
The average age of my patients was 45 years. Treatments ranged from -7.50 to +3.50D. I examined patients on postoperative days 1 through 4. The average pachymetry was 537µm, with a corneal diameter of 11.7mm and keratometry readings of 44.6µm. The average flap thickness was 61 ±13µm. The flap diameter was 9.4 ±0.2mm, with an ablation zone of 8.9 ±0.5mm.
My Epi-LASIK patients all receive a fluoroquinolone eye drop the night before and on the day of the procedure. Just before surgery, I apply a drop of anesthetic. As I noted earlier, I realized over time that exposing the epithelium to as little anesthetic as possible makes it more viable.
With the Epi-K, I use a ring with a 7.5-mm stop displaced nasally for myopic treatments and a slightly larger stop (8.0mm) for hyperopic treatments. These parameters yield a relatively wide average hinge width of 6.6mm. A larger hinge makes it easier to reposition the flap, but then the surgeon must make sure there is adequate room for the ablation, especially with large hyperopic or customized ablations.
I mark the epithelium just as I would for a LASIK case. Next, I place a drop or two of Genteal preservative-free gel (Novartis Ophthalmics, Inc., Duluth, GA) on the eye and on the separator to ensure that the epithelial surface is well lubricated for the forward pass. I initially irrigated copiously with BSS, as other Epi-LASIK surgeons recommended, but found that the BSS was detrimental to the health of the epithelium. I much prefer the more gentle lubricating properties of the gel.
Before placing the suction ring on the eye, I engage the foot pedal in position 3 and advance the separator just until its front edge is at the opening of the suction ring. In this manner, I reduce the total suction time to about 33 seconds.
Next, I place the suction ring on the eye, obtain suction, and advance the separator using foot pedal position 1 for a few seconds—just until the epithelium starts lifting onto the separator. I move to position 3 until the stop is reached. When the forward pass is complete, I switch to low vacuum, place additional Genteal gel on the eye, and begin the reverse pass. Thorough lubrication is essential to preventing friction during both passes of the Epi-K. Once the separator has completely cleared the epithelium, I turn off the suction and lift the device's head from the nasal to the temporal side, in the opposite direction of the flap, in order not to displace it.
The epithelial flap should be gently folded back in an accordion's shape using a blunt, nonirrigating instrument. It is important to remember that the epithelial tissue is much more delicate than a stromal flap. Attempting to lay the entire flap back like a LASIK flap will devitalize the cells, as I learned during my initial cases. I dry the surface of Bowman's membrane both with a Weck-cel sponge (Medtronic Xomed Ophthalmics, Inc., Minneapolis, MN) and a blunt spatula sweep, and then I perform the excimer laser treatment. In this study, all eyes were treated with customized ablations using the Star S4 laser with Customvue (Visx, Incorporated, Santa Clara, CA).
After the laser application, I apply a round, frozen Weck-cel sponge to the bed for approximately 45 seconds. I prefer this technique over chilled BSS, again because the BSS somewhat devitalizes the epithelium. I apply only a very small amount of BSS at the end of the case to coat the bed so that the flap will slide into place. Using a blunt spatula, which should grasp the leading edge of the epithelium, I gently reposition the epithelial flap without touching the central part of the cornea at all. The other end of the spatula can be used to pull out any portion of the flap that curls under.
It is important to let the flap dry for approximately
2 minutes for better adherence before placing the bandage contact lens. I have typically placed the contact lens nasally and draped it temporally so as not to displace the flap. I like the suggestion of several of my colleagues, however, to put the lens on the center of the cornea, inverted, and then gently fold it back over the cornea with a Weck-cel sponge in order to avoid any air bubbles between the epithelium and the lens.
Thus far, I have not experienced any intra- or postoperative flap complications with the Epi-K. If I were to encounter a partial flap, my inclination would be to remove the rest of the epithelium and convert to PRK, but that decision would depend on how much of the flap remained.
In the 25-eye cohort described here, 100% of the flaps were categorized as excellent. The Epi-K epithelial separator consistently makes an elegant flap. The surgeon's job is not to damage that flap with overhandling, manipulation, or chemical devitalization of the epithelial cells.
Postoperatively, I instruct patients to use an NSAID q.i.d. for 5 days and a steroid q.i.d. for 1 month. I also prescribe vitamin C for 3 months, a fluoroquinolone q.i.d. until the bandage lens is removed, oral pain medication, and four tablets of Ambien (G.D. Searle & Co., Peapack, NJ) so that patients sleep well for the first
4 nights. I had been giving comfort drops (diluted proparacaine) but eliminated them from my postoperative pain regimen because patients never needed them.
The pain my patients experienced was more than they would with LASIK but significantly less than with PRK or LASEK. During each day's examination, my co-investigators and I asked patients to rate the severity of the pain they experienced over the worst 2 hours during the previous day. On a scale of 1 to 10, the majority of patients ranked the pain at between 2 and 4, although some were as high as 7 on day 1. By day 2, no one reported a pain score above 3. On the third day, the vast majority of patients said they experienced no pain or only level 1 pain.
The frozen Weck-cel sponge at the end of the case and a tightly fitting bandage contact lens decrease the number of pain complaints. I leave the contact lens on for at least as long as I would after a PRK procedure and usually 1 or 2 days longer. Typically, I remove the bandage lens between days 5 and 7 for Epi-LASIK patients. Mark Swanson, MD, of Agua Prieta, Mexico, has recently started changing the bandage contact lens on day 3 to promote healing, and I am considering doing the same.
I have found patients' visual recovery following Epi-LASIK to be somewhat better than with other surface ablation procedures, although patients still do not experience the “wow” effect of LASIK. In my experience, far more patients are conservative, safety-conscious, and quite willing to trade LASIK's convenience for Epi-LASIK's safety.
There are several ways to measure visual recovery postoperatively. One is the restoration of functional vision indicated by the patient's returning to work. In this study, only two of the 25 eyes were unfit for work by day 4, compared with a typical timeframe of day 6 for PRK patients. Certainly, it is fair to counsel patients that their vision during the first postoperative week will be functionally fuzzy. For the occasional Epi-LASIK patient who absolutely must return to work the day after surgery, I will treat one eye at a time.
In terms of visual acuity, the results were superb. Although all of the subjects had complex refractions, their average postoperative UCVA on day 1 was 20/60. By day 4, it had improved to 20/40, with a range of 20/25 to 20/100. One month postoperatively, 48% of the eyes had gained one or more lines of BCVA compared to their preoperative BCVA, and subjects' average visual acuity was 20/25, with a range of 20/15 to 20/40. These results do not provide a complete picture of distance vision, because a few eyes were targeted for monovision rather than emmetropia.
Although I typically have an enhancement rate of approximately 10%, I have not had to re-treat any of these eyes. No problems due to hydration occurred. Excessive hydration (with BSS or Genteal) of the stroma has been associated with LASIK undercorrections. In Epi-LASIK, however, the surgeon is hydrating Bowman's membrane rather than the stroma, so there is no reduction in the laser's effect.
One can also measure visual recovery by the health of the epithelial flap. In this study, we ranked the appearance of the epithelium, with 0 being excellent and 5 being about the same as a LASEK flap. On day 1, the average was 1.2; on day 3, the average was 1.6, with 4 being the worst noted on either day. All flaps were categorized as excellent at the conclusion of surgery. The amount of overhanging or stretched edge noted was 0 to 2mm, with the average being 1mm. In my hands, the Epi-K produces a flap with much less stretch than most Epi-LASIK surgeons have reported.
The most important factor in obtaining good visual recovery over the first 3 to 4 days following surgery is strict adherence to the less is more mantra. By avoiding epithelial manipulation, one can achieve excellent visual results.
Epi-LASIK's ROLE IN MY PRACTICE
As I noted earlier, Epi-LASIK is replacing PRK in my practice. My patients experience less pain with the former, and their visual recovery is earlier and more predictable. Just as important is the psychological impact of talking to patients about Epi-LASIK rather than PRK. Anyone who is a proponent of surface ablation recognizes that PRK, despite its advantages, is an older procedure that has some negative connotations for patients. Being able to treat the ocular surface without using that terminology allows me to have a different conversation with the patient.
I plan to transition soon to 100% customized ablations. With that change, I will likely raise my surgical fees across the board. Patients will pay the same fee whether they have LASIK, Epi-LASIK, or conductive keratoplasty. Even the refractive IOL procedures I perform, although more expensive for the patient due to OR and lens costs, will not result in a greater financial gain for my practice. That way, patients can feel confident that I am recommending the procedure that is truly best for their eyes and visual needs, rather than one that makes the highest profit.
Initially, I will perform Epi-LASIK on patients for whom I would have chosen surface ablation anyway. As I grow more comfortable with patients' postoperative recovery, it may become my procedure of choice. I can envision a time in the not-too-distant future when only the extremely pain-averse or convenience-minded will have LASIK in my practice.
I think most of us refractive surgeons do not want to hear that LASIK may not be the best procedure in the age of wavefront technology. We want to do the procedure that is more convenient and less painful for patients. It just may turn out that Epi-LASIK is not only safer but provides better wavefront outcomes for our patients, and such a revelation will force all of us to question which procedure should be our first choice.
H. L. “Rick” Milne, MD, is in private practice at The Eye Center in Columbia, South Carolina. He states that he holds no financial interest in the products or companies mentioned herein. Dr. Milne may be reached at (803) 256-0641; email@example.com.