How do surgeons approach enhancements in refractive surgery patients?
Two practitioners share the pros and cons of their preferred techniques.
As laser refractive surgery enters its third decade of widespread use in the U.S., an increasing number of patients are now returning for enhancements. LASIK patients, in particular, present the dilemma of how to approach the enhancement. While some surgeons prefer to lift the previous flap or to cut a new flap, others prefer surface treatment to avoid the complications of creating or lifting a flap. There are numerous advantages and pitfalls to both techniques. This month, Dr. Thomas Boland and Dr. Damien Goldberg discuss the pros and cons of lifting the old flap and using surface treatment. We hope you enjoy the discussion.
Kenneth A. Beckman, MD, FACS
OSN CEDARS Debates Editor
Flap lift enhancement
When a patient presents with residual or subsequent refractive error after prior LASIK, there are several surgical options available to correct that refractive error. Flap lift enhancement, surface ablation, recutting a flap or side cutting a new flap in the old bed have all had their proponents, and each offers distinct advantages and disadvantages. As my career has advanced, my preference has evolved over time. Early on, I performed some flap recuts but quickly abandoned this as an option because of the risk of crossing the plane of the prior cut and the development of slivers of tissue. I proceeded to flap lift in virtually all cases and have successfully lifted flaps more than 15 years old without significant difficulty. Later, I began to perform surface ablation on top of the old flap in selected cases and still perform this sometimes, but my main preference remains flap lift when possible.
We are all familiar with the various reasons why patients choose LASIK vs. surface ablation for their primary procedure. Chief among these reasons are the rapid visual recovery and improved comfort that the LASIK procedure offers, and the same factors persist in the decision for an enhancement procedure. These patients frequently have high visual expectations, hence the need for the enhancement, and they expect the same type of experience and “wow” factor that their initial surgery offered. This is simply not possible with a surface enhancement. Lifting the flap for the enhancement can maintain the corneal surface integrity and offer the rapid visual recovery and comfort that these patients expect.
The main critique of flap lift enhancement is the risk of developing epithelial ingrowth under the flap after the procedure. Most studies place this risk at 6% to 8%, with more recent studies showing a trend toward lower rates with more modern flap geometry. Personal experience has shown that most cases of ingrowth remain localized and asymptomatic and can often simply be observed. Review of the literature and my own patients has shown that only roughly 2% of enhancement patients will require intervention for their ingrowth. Meticulous, sharp dissection of the epithelium at the flap edge helps to lower this risk, as has the development of femtosecond laser flaps, with a sharper angle of entry to the flap edge. Newer lasers, with the ability to create side cuts of greater than 90°, should continue to reduce this phenomenon.
The primary alternative to flap lift is surface ablation, with all its attendant problems. Patients often remain uncomfortable for several days after the procedure, and the delay in visual recovery is disconcerting to patients who have come to expect a rapid result. Occasionally, we see patients with a prolonged delay in recovery of uncorrected and best corrected visual acuity. This is most often manifested as development of with-the-rule astigmatism and can take many exasperating weeks to resolve as the epithelium slowly remodels. Also, any epithelial insult after prior flap creation raises the risk of diffuse lamellar keratitis, which, if not properly managed, can be visually devastating.
Given the pros and cons of each procedure, we find that most patients, with proper education and understanding, choose flap lift enhancement when offered. As the percentage of older microkeratome-created flaps continues to decline, I find it becomes easier than ever to offer this modality. Do the same, and your patients will thank you for it.
Now that it has been 30 years since some of our earliest LASIK cases, more of us clinicians are seeing patients return to our offices exploring LASIK re-treatments and alternative vision options. Re-treating LASIK can be effective when done safely. The question that remains is, if the cornea look stable, what is the best way to re-treat these patients? Do we lift the flap or perform surface ablation on the flap?
Oftentimes when patients return to my office for enhancements, patients recall that they had LASIK before but do not remember the details to their surgery. They know they loved the instantaneous visual outcome, but few can recall the refractive surgical history that we need. Information such as their previous glasses prescription, type of laser ablation, or the name or set depth of the device that created their LASIK flaps would be useful to know. The reality is that recovering old records can be challenging when they are 10 years old and in a paper chart that has been sent to storage.
Even if pachymetry demonstrates adequate corneal thickness, it can be tough to always judge what aspect of the cornea is the residual bed on anterior optical coherence tomography and what is the LASIK flap. Unless the patient is a good historian, topography, Orbscan (Bausch + Lomb) or Pentacam (Oculus) information is not always useful in predicting if multiple excimer treatments were performed. These little details are monumental when identifying risk factors that could destabilize the corneal architecture and cause iatrogenic keratoectasia. To reduce ectasia, I prefer to perform surface ablation.
Another risk of lifting flaps during laser correction is epithelial ingrowth. A 2005 study demonstrated epithelial ingrowth may be clinically significant in 37.1% of patients. Epithelial ingrowth tends to occur more when blunt dissection is used to open flaps. Ingrowth is greater because more cells are introduced into the interface. In recent years, flap lifting requires more blunt dissection because flaps generated by femtosecond laser have more adhesions. Epithelial ingrowth also occurs more frequently 3 years after primary LASIK. Epithelial ingrowth can usually be managed with steroids and cell scrapping once the flap is lifted back. However, when managing more difficult ingrowth cases, sometimes the flap must be sutured down or the flap must be removed altogether to prevent corneal flap or corneal bed melts.
Surface ablation is not likely to have corneal melts but is not without its own risks. Haze formation has been reported in the literature after any surface ablation treatment. The risk of haze is greater when laser corrections are for treatments greater than 2 D and for enhancements soon after primary LASIK treatments. Fortunately, haze can be safely minimized by using topical mitomycin C 0.002% after re-treatment with surface ablation. Most of my surface ablation enhancements are usually less than 2 D and performed years after their primary surgery. I still like using MMC 0.002% for 12 to 30 seconds after laser treatments. If haze presents postoperatively, I have found frequent application of postoperative steroid drops effective at resolving these presentations.
Some other major advantages to surface ablation is that it can be the laser treatment of choice in smoothing out and managing old buttonholes or slightly deformed flaps that may have occurred during primary LASIK and PRK cases. Surface ablation is also my treatment of choice in enhancing vision correction when managing RK patients.
If there were one drawback to surface ablation, it would be the transient blurred vision and discomfort patients may experience. I continue to find with adequate counseling and patient preparation, these setbacks are temporary. At the end of the day, surface ablation is my procedure of choice for re-treating LASIK patients. I achieve great visual correction results in the safest manner possible.