LASIK is the most widely used refractive surgical technique due to its safety and effectiveness, quick visual recovery, and minimal side effects. However, it is not exempt from complications, both during surgery and in the years following. Therefore, it is advisable to frequently monitor patients who undergo this procedure to enable early diagnosis and treatment of complications if appropriate.
A 39-year-old man with no meaningful personal or family history of ophthalmic problems presented to our practice with an interest in refractive surgery. In his right (dominant) eye, UCVA was 0.05, improving to 1 when corrected with -0.50 X 90º -3.00 D. In the left eye, UCVA was 0.4 and improved to 1 when corrected with 0.25 X 180º -1.75 D.
An exploration of the anterior segment of both eyes showed transparent corneas with endothelial guttata, wide anterior chambers, and incipient corticonuclear scleroses of the lenses. The rest of the anterior segment and the posterior segment presented no meaningful alterations in both eyes. His intraocular pressure (IOP) was within the normal range. No corneal pathologies were found on corneal topography (Orbscan; Bausch + Lomb) of the right (Figure 1) and left (Figure 2) eyes, and his endothelial cell count with specular microscopy (Noncon ROBO; Konan Medical, Inc.) was 2,193 cells/mm2 in the right eye (Figure 3) and 1,767 cells/mm2 in the left (Figure 4). Aiming to correct the refractive defect of both eyes, LASIK was planned using a lamellar microkeratome (Amadeus; Ziemer Group) to create the corneal flap; however, surgery was postponed for 2 months, as the patient contracted moderate bilateral adenoviral conjunctivitis without corneal involvement.
Surgery was completed without complications, and dexamethasone drops twice daily for 1 week, artificial tears applied hourly, and hygiene measures were prescribed after surgery. At the initial follow-up visit, the patient’s UCVA was 1.2 and 0.9 in his right and left eyes, respectively. The cornea was transparent, the flap was well positioned, and no alterations were noted in the corneal interface.
One month after surgery, the patient’s bilateral UCVA was 0.8 and did not improve with refractive correction; UCVA in his left eye was 0.9. Corneal exploration showed linear invasion of epithelial cells at the 9-o-clock position in the right eye and at the 5-o’clock position in the left (Figure 5). Treatment with artificial tears was intensified, and the patient was asked to apply drops more frequently than once per hour. At the following visit, 1 month later, the patient reported a decrease in visual acuity in his right eye compared with his left. UCVA was 0.8 in the right eye but improved to 0.9 with a correction of 1.25 X 175º +0.25 D. In the left eye, UCVA was 1 and accepted a refraction of -0.75 X 95º +0.25 D. A higher interface of epithelialization up to the edge of the pupillary area was observed in the anterior segment of the right eye (Figure 6), causing the decrease in visual acuity.
We decided to lift the corneal flap and perform an enhancement to clean the epithelial ingrowth from the interface. We also planned to place a corneal suture to prevent the epithelium from invading the area again. During the procedure, the accumulation of epithelial cells along the internal edge of the flap and in the interface of the flap was cleaned using a hockey-stick knife. It is important to clean the entire flap properly, identifying the usually wide entrance area. In this case, the corneal flap was repositioned and the edges were sutured using three interrupted 10-0 nylon sutures. Tobramycin drops, dexamethasone every 6 hours, and dexamethasone-chloramphenicol eye ointment at night were prescribed.
One day after surgery, UCVA in the right eye was 0.2 and did not improve with any correction. The IOP was 12 mm Hg, and a central epithelial defect was observed even though the flap was well positioned and the interface was clean. We placed a bandage contact lens and informed the patient it would remain on the eye until the cornea reepithelialized. The patient started topical treatment with tobramycin and dexamethasone eye drops twice daily, ofloxacin eye drops every 6 hours, and one-dose artificial tears every 2 hours for 3 weeks.
This regimen produced good progress without complications, and, 1 month after surgery, the patient’s UCVA improved to 0.9 in his right eye. When corrected with -2.25 X 135º +0.50 D, his visual acuity was 1. The cornea was transparent, and there was no epithelial ingrowth. We thus removed the three corneal sutures to check the astigmatism they had produced (-2.23 X 135º +0.50 D). At the last postoperative follow-up, 6 months after cleaning the epithelial ingrowth, the patient’s UCVA was 1.2 in his right eye and 1.0 in his left, and the IOP was 14 mm Hg. In his right eye, the cornea was transparent and the flap was well positioned, with no signs of epithelial ingrowth in the interface. A small area of fibrosis was observed in the temporal quadrant (Figure 7).
Epithelialization of the interface, which can occur after flap creation with a mechanical microkeratome, is caused by the proliferation of epithelial cells between the stroma and the flap. If the layer of epithelialization reaches a thickness between 40 and 60 μm and its diameter is greater than 2 mm, it can be compounded by flap keratolysis or corneal melting.1 Epithelialization of the interface occurs due to an invasion of the flap by the peripheral corneal epithelium, probably secondary to poor sealing of the flap edge or due to migration of epithelial cells under the flap.2-4 It is more frequent in patients with seborrheic blepharitis, in those who have an epithelial defect at the time of the intervention, and in patients who require retreatment by lifting the previous flap;3 it affects between 1% and 15% of eyes treated with LASIK.2,4 Placing a bandage contact lens after surgery can reduce the incidence of epithelial ingrowth in patients with a higher risk for this complication.
In this case, we did not see any epithelial defect after surgery; however, the patient had presented with adenoviral conjunctivitis 2 months before the surgery without corneal involvement. If we had used a femtosecond laser instead of a mechanical microkeratome to create the corneal flap, there would have been less mechanical trauma; a lower rate of epithelialization of the interface;5 and, by using a vertical sidecut incision, no epithelial cell migration. These factors may decrease the risk for post- LASIK enhancement and epithelial ingrowth.
Treatment of epithelialization is controversial, as there is no ideal treatment. Therapeutic abstention is even suggested, mainly due to the surgical risks associated with reoperations, including a higher incidence of epithelialization, irregular astigmatism, and small tears in the flap.6-8 Therefore, if there are isolated nests of epithelial cells in the lamellar interface but they do not progress and do not affect vision, they do not require treatment. However, if the epithelium progresses toward the visual axis, producing a decrease in visual acuity and inducing irregular astigmatism, or it triggers melting of the overlying flap, it must be removed by lifting the flap, cleaning the interior surface and the stromal bed, and repositioning the flap.
Some surgeons also remove the peripheral corneal epithelium to facilitate the adherence of the flap before the epithelial edge progresses to the edge of the flap.8 Other surgeons correct recurrent epithelial ingrowth by repeatedly lifting and scraping, with or without a flap suture, or with fibrin glue at the edge of the flap.9,10
Monitoring patients frequently after LASIK enables early detection of postoperative complications that may otherwise go unnoticed, as they are virtually asymptomatic. If epithelial ingrowth appears in the interface, causing a decrease in visual acuity or inducing irregular astigmatism, it must be treated by carefully cleaning the interface and the interior edge of the corneal flap and subsequently suturing to avoid further penetration of epithelial cells. With this surgical option, after the removal of the corneal sutures, this patient’s visual results and surgical correction were satisfactory.
Daniel Elies, MD, is in private practice in the Cornea and Refractive Surgery Unit at the Instituto de Microcirugía Ocular, Barcelona, Spain. Dr. Elies may be reached at tel: +34 93 253 15 00; fax: +34 93 417 13 01; e-mail: firstname.lastname@example.org.
Oscar Gris, MD, PhD, is in private practice in the Cornea and Refractive Surgery Unit at the Instituto de Microcirugía Ocular, Barcelona, Spain. Dr. Gris may be reached at e-mail: email@example.com.
Jose L. Güell, MD, PhD, is Director of the Cornea and Refractive Surgery Unit of the Instituto de Microcirugía Ocular, Barcelona, Spain, and an Associate Professor of Ophthalmology at the Universitat Autonoma de Barcelona. Dr. Güell may be reached at tel: +34 93 253 15 99; fax: +34 93 417 13 01; e-mail: firstname.lastname@example.org.
Felicidad Manero, MD, is in private practice in the Cornea and Refractive Surgery Unit at the Instituto de Microcirugía Ocular, Barcelona, Spain. Dr. Manero may be reached at e-mail: email@example.com.
Paula Verdaguer, MD, is in private practice in the Cornea and Refractive Surgery Unit at the Instituto de Microcirugía Ocular, Barcelona, Spain. Dr. Verdaguer may be reached at e-mail: firstname.lastname@example.org.
The authors state that they have no financial interest in the materials presented in this article.
- Walker MB, Wilson SE. Incidence and prevention of epithelial growth within the interface after laser in situ keratomileusis. Cornea. 2000;19(2):170-173.
- Fournié PR, Gordon GM, Dawson DG, et al. Correlation between epithelial ingrowth and basement membrane remodeling in human corneas after laser-assisted in situ keratomileusis. Arch Ophthalmol. 2010;128(4):426-436.
- Saeed A, O’Doherty M, O’Doherty J, et al. Analysis of the visual and refractive outcome following laser in situ keratomileusis (LASIK) retreatment over a four-year follow-up period. Int Ophthalmol. 2007;27(1):23-29.
- Jun RM, Cristol SM, Kim MJ, et al. Rates of epithelial ingrowth after LASIK for different excimer laser systems. J Refract Surg. 2005;21(3):276-280.
- Güell JL, Elies D, Gris O, et al. Femtosecond laser-assisted enhancements after laser in situ keratomileusis. J Cataract Refract Surg. 2011;37(11):1928-1931.
- Lyle WA, Jin GJ. Interface fluid associated with diffuse lamellar keratitis and epithelial ingrowth after laser in situ keratomileusis. J Cataract Refract Surg. 1999;25(7):1009-1012.
- Stulting RD, Carr JD, Thompson KP, et al. Complications of laser in situ keratomileusis for the correction of myopia. Ophthalmology. 1999;106(1):13-20.
- Dawson DG, Kramer TR, Grossniklaus HE, et al. Histologic, ultrastructural, and immunofluorescent evaluation of human laser assisted in situ keratomileusis corneal wounds. Arch Ophthalmol. 2005;123(6):741-756.
- Wang MY, Maloney RK. Epithelial ingrowth after laser in situ keratomileusis. Am J Ophthalmol. 2000;129(6):746-751.
- Asano-Kato N, Toda I, Hori-Komai Y, et al. Epithelial ingrowth after laser in situ keratomileusis: clinical features and possible mechanisms. Am J Ophthalmol. 2002;134(6):801-807.