Laser treatment of epithelial ingrowth after LASIK shows promise
While most LASIK procedures are problem-free, one type of complication that can occur occasionally is something called epithelial ingrowth.
Researchers in Spain have found an innovative way to treat epithelial ingrowth that is easier and less invasive than previous corrective measures and decreases the risk of the problem coming back.
Basic corneal anatomy
The front surface of the eye – the cornea – has two primary cell layers. The thin outer layer is called the epithelium. This layer of fast-growing cells makes up about 15% to 20% of the cornea's overall thickness and is roughly 100 microns thick.
The thicker underlying layer of the cornea is called the stroma. Comprised of slower-growing cells, the stroma accounts for approximately 80% to 85% of the overall corneal thickness, and is typically about 450 microns thick.
The flap of corneal tissue created in LASIK surgery is usually 120 to 150 microns thick and contains both epithelial and stromal cells.
What is epithelial ingrowth?
Epithelial ingrowth is the growth of epithelial cells under the corneal flap after the flap is replaced at the end of the LASIK procedure. It can be caused by a few live epithelial cells being trapped under the flap during surgery, or epithelial cells may grow under the flap at its margin during the healing process after surgery.
Epithelial ingrowth may take several weeks to become apparent. Depending on the severity of the ingrowth, it can cause blurred or distorted vision and eye discomfort.
The incidence of epithelial ingrowth can vary widely, depending on surgical techniques, the method used to create the flap and whether the LASIK is a first-time procedure or a retreatment (also called an enhancement procedure). Estimates of the occurrence of epithelial ingrowth after LASIK range from less than 0.5% to 15% of cases, based on these variables. (1)
Treatment of epithelial ingrowth.
The traditional treatment for epithelial ingrowth is to surgically re-lift the flap and mechanically remove the epithelial cells underneath it. The exposed "bed" of corneal stroma is then treated with a dilute alcohol solution to keep epithelial cells from growing back, and the flap is replaced.
In some cases, the surgeon may apply a bandage contact lens to help seal the flap margin and decrease the likelihood of epithelial cells again growing under the flap margin. In severe cases, the flap may actually be sutured down.
Though this traditional "lift and clean" method of treatment is usually successful, the risk of recurrence of epithelial ingrowth after the procedure is relatively high, since the stromal bed is again exposed, as it was during the LASIK procedure. Also, in some cases, it can be difficult for the surgeon to lift a flap that has adhered to the underlying cornea as part of the healing process after LASIK.
A new, less invasive technique
If epithelial ingrowth could be treated without the need to re-lift the corneal flap, the risk of recurrence of the problem would certainly be less.
To explore this option, researchers in Spain experimented with a tool that's very familiar with eye surgeons – the Nd:YAG laser. Commonly referred to as the "yag laser," this low-energy laser is used in certain types of cataract and glaucoma surgery.
For the past several years, Jorge L. Alio, MD and his colleagues have been using the Nd:YAG laser to effectively and safely treat epithelial ingrowth without lifting the LASIK flap.
Though settings on the laser must be adjusted for this new use, no modifications of the laser itself are required and the laser can continue to be used for cataract and other procedures as well.
Over a 4-year period, the researchers report they have successfully treated more than 200 eyes affected by post-LASIK epithelial ingrowth with the new laser procedure.
In most cases, only a single session of the Nd:YAG laser treatment is required for successful treatment. In some cases, a second session is required. This second session is usually scheduled three weeks after the first treatment.
Results
In an article published in Refractive Eyecare (2), Dr. Alio reports that after the laser treatment, epithelial patches under the flap disappeared in 80% of the eyes, and visual acuity improved by at least one line (on a standardized eye chart) in 60%.
There have been no complications from the procedure and no recurrences of the ingrowth over a two-year follow-up period, according to Dr. Alio. (3)
Best when performed early
Dr. Alio feels the Nd:YAG laser procedure is most effective in treating epithelial ingrowth and preventing it from progressing to a sight-threatening stage if it takes place relatively soon after it is detected. If epithelial ingrowth is found during routine follow-up exams after LASIK, he recommends treating the condition approximately one month after the LASIK procedure.
He cautions that the Nd:YAG should be reserved for peripheral epithelial ingrowth and should not be used if the epithelial cells are directly within the patients line of sight, as there may be some risk of corneal scarring from the treatment.
The treatment of the future?
Dr. Alio recommends the new Nd:YAG laser procedure as an alternative to the traditional method of treating epithelial ingrowth, noting that the laser procedure is simple, non-invasive and effective, and has "an excellent risks/reward ratio for both doctor and patient."
SOURCES:
1. Tips for preventing and treating epithelial ingrowth after LASIK. Ocular Surgery News; Europe/Asia-Pacific Edition. June 2007.
2. Treating epithelial ingrowth: An easy, effective alternative to flap lifts. Refractive Eyecare. Vol 12, No 6. June 2008.
3. Treatment of laser in situ keratomileusis interface epithelial ingrowth with neodymium:yttrium-aluminum-garnet laser. Am J Ophthalmol. Vol 145, No 4. April 2008.
Last updated: February, 2010
