Read Refractive Surgery Outlook

Removing Epithelial Ingrowth: Laser vs. Glue

By Tony Hampton

Incidence of Epithelial Ingrowth

In a study that reviewed all LASIK procedures performed by a single U.S. surgeon over a 3.5-year period, there were no cases of visually significant epithelial ingrowth in 3,866 primary LASIK procedures. There were, however, 15 cases of epithelial ingrowth (2.3 percent) in the 646 flap-lift retreatments he performed.¹ A study conducted in Turkey in which all flaps were created with a femtosecond laser reported just two eyes with clinically significant epithelial ingrowth in 6,415 primary procedures.² But of the 108 eyes in that group that underwent relift for enhancement, two eyes (2 percent) experienced clinically significant epithelial ingrowth.

David R. Hardten, MD, FACS, a founding partner and director of clinical research at Minnesota Eye Consultants in Minneapolis, attributes the low frequency of post-LASIK epithelial ingrowth to several factors. First, surgeons have become skilled at detecting epithelial basement membrane dystrophy (EBMD), an important risk factor for epithelial ingrowth, in preoperative examinations. (Patients with EMBD can be treated with PRK instead of LASIK.) In addition, because late flap lifts, (those performed more than three years after a primary LASIK procedure) are associated with an increased incidence of clinically significant epithelial ingrowth, some surgeons now use surface ablation to enhance these eyes to reduce the  possibility of epithelial ingrowth.¹

Both Dr. Hardten, who is also an adjunct associate professor of ophthalmology at the University of Minnesota in Minneapolis, and Jorge Alió, MD, PhD, medical director of VISSUM Ophthalmology Corp. in Alicante, Spain, note that femtosecond lasers that produce planar flaps with 90-degree edges also appear to significantly reduce the incidence of ingrowth, presumably as a result of enhanced flap geometry.²

When it does occur, most epithelial ingrowth is stable, located away from the visual axis and is visually insignificant, requiring only monitoring at appropriate intervals. Treatment is required only when epithelial cells encroach on the visual axis and cause or threaten to cause visual symptoms.

Nd:YAG Laser Technique

Dr. Alió, who is also professor and chairman of ophthalmology at Miguel Hernandez University in Alicante, treats most cases of clinically significant epithelial ingrowth with an Nd:YAG laser technique he developed.³ He treats any ingrowth that affects a patient’s best corrected visual acuity, and prefers to treat immediately upon detection.

He says all patients who undergo a flap relift for enhancement should be examined for epithelial ingrowth two to three weeks after the enhancement procedure. If ingrowth is found at this time, it can be treated with the Nd:YAG laser before the cells have a chance to proliferate.

Dr. Alió does not lift the flap when using the YAG laser. Instead, he applies the laser directly to the nests of epithelium in the interface, using the lowest level of energy capable of creating a cavitation bubble under the flap. He creates as many laser spots as necessary to cover the affected area. He notes that the cavitation bubbles do not need to be in contact with each other in order to accomplish complete removal of the epithelium. In addition to direct destruction of epithelial cells that absorb the laser energy, the shock wave produced induces apoptosis in nearby cells. As a result, all of the interfacial epithelial cells are destroyed, with minimal collateral damage.

In order to prevent epithelial ingrowth recurrence, Dr. Alió makes sure to find and treat the fistula through which the epithelium originally gained entry.

Ingrowth Removal Using Fibrin Glue

Dr. Hardten’s go-to procedure involves preparing the anterior epithelial surface by removing a 1- to 2-mm band of epithelium around the flap edge, lifting the flap, manually removing the ingrown cells from the stromal bed and posterior surface of the flap, and then sealing the interface with fibrin glue.⁴

For Dr. Hardten, a key issue is preventing recurrence. He notes that, “The same etiology that allowed the epithelium to enter the interface before the procedure is still present because after a relift—whether for refractive enhancement or to remove ingrown epithelium—a tight seal between the flap and the stromal bed may not form quickly enough to prevent epithelium from insinuating itself beneath the flap.”

For Dr. Hardten, the fibrin adhesive acts like a barrier, allowing time for the stroma of the flap and the bed to bind tightly together before the epithelium can enter. The problem with sutures is that in addition to sealing wound edges at points where the sutures are located, they also create areas of puckering between sutures, and these may allow entry to epithelial cells. He uses sutures only when a tissue adhesive may not provide an adequate barrier, such as areas of fibrotic tissue with elevation at the flap edge.

For small, circumscribed pockets of epithelial ingrowth that seem stable but are sufficiently elevated to produce visual symptoms, Dr. Hardten uses Dr. Alió’s Nd:YAG laser technique. However, he prefers manual epithelial cell removal and sealing with fibrin adhesive for cases in which the nests of ingrown cells appear to be enlarging.

Follow-up

After treatment, Dr. Hardten places a bandage soft contact lens on the eye and prescribes antibiotic, steroid and NSAID drops, using a regimen similar to that prescribed for PRK patients. He sees patients the day after the procedure and again two to three weeks later. Typically at that point, the glue has been resorbed and the bandage lens can be removed. If there is glue remaining, the bandage lens may stay on the eye for another one to two weeks.

Massive Ingrowth

When the epithelial ingrowth is massive or the result of a regrowth of epithelium that was previously removed, both Dr. Hardten and Dr. Alió lift the flap and manually debride both sides of the interface. Dr Alió notes that alcohol and mitomycin should never be used; the former causes corneal scarring, and the latter is ineffective. Instead, he uses distilled water (which is hypotonic) to loosen the cells from the stroma, treating the stroma on both sides of the interface.

In his words, “I drop distilled water onto the flap until it curves like a papyrus, at which point I know that I have produced corneal edema and detachment of the epithelial cells.” He then manually removes the loosened tissue and sutures the flap with seven interrupted sutures, having earlier used an RK marker to denote the suture positions. After suturing, a bandage contact lens is applied. Sutures are removed 10 to 15 days later.

Dr. Alió adds, “When using this procedure, it is critical to let the patient know that his or her vision will be significantly decreased for approximately the next four weeks. It is also important to alert the patient to possible discomfort from the sutures.”

But he says there is an upside: “You never see a relapse.”

References

1. Caster AI, Friess DW, Schwendeman FJ. Incidence of epithelial ingrowth in primary and retreatment laser in situ keratomileusis. J Cataract Refract Surg. 2010;36(1):97-101.

2. Kamburoglu G, Ertan A. Epithelial ingrowth after femtosecond laser-assisted in situ keratomileusis. Cornea. 2008;27(10):1122-1125.

3. Ayala MJ, Alió JL, Mulet ME, De La Hoz F. Treatment of laser in situ keratomileusis interface epithelial ingrowth with neodymium:ytrium-aluminum-garnet laser. Am J Ophthalmol. 2008;145(4):630-634.

4. Anderson, N.J., Hardten, D.R. Fibrin Glue for the Prevention of Epithelial Ingrowth after Laser in Situ Keratomileusis. J Cataract Refract Surg. 2003; 29(7):1425-1429.

Financial disclosures

Dr. Hardten is a consultant to Abbott Medical Optics.

Dr. Alió reports no financial interest in the subject matter discussed.

Tony Hampton is a medical writer based in New York City.