Online Photo Diagnosis

By William Townsend, OD, FAAO

The individual in this photo presented six months after laser-assisted in-situ keratomileusis (LASIK) with bilateral epithelial ingrowth. This is a relatively uncommon finding. In approximately 1 percent of eyes that have undergone LASIK, corneal epithelium gains egress into the flap-bed interface and may grow to significant proportions. This phenomenon is associated with lower endothelial cell counts, thinner flap thickness, and enhancement.

Courtesy of Janet Townsend

Courtesy of Janet Townsend

Following LASIK, healing of the ocular surface proceeds via epithelial growth. At the same time, collagen fibrils grow in the interface between the flap and bed and create adhesion that proliferates over time. The flap-bed adhesion never becomes “permanent,” and years after the initial procedure the flap can still be peeled away from the bed. Re-innervation of the flap is also a gradual process. Calvillo et al reported that one year after LASIK, nerve density is only 50 percent of that found in un-operated eyes.¹

Epithelial ingrowth typically occurs by one of two basic mechanisms. Epithelial invasion occurs shortly after the initial LASIK procedure. Epithelial cells situated at the margins of the flap begin to grow into the potential space created by the flap-bed interface. Asano-Kato N et al reported on factors that contribute to this condition. They found that flaps created by microkeratomes that cut obliquely heal more slowly and thus are more prone to epithelial ingrowth. Keratomes that cut flaps vertically, such as the femtosecond laser, are less prone to be associated with ingrowth.²

Epithelial implantation usually occurs after enhancement procedures. Spatulas are regularly used to lift the flap prior retreatment. In some instances, epithelial cells or fragments may inadvertently be transferred to the surgical bed where they replicate and form sheets of epithelium. The incidence of epithelial ingrowth post-enhancement is reportedly higher than that after initial LASIK. Wilson and Santhiago described significant reduction in the incidence of enhancement-induced ingrowth using the flaporhexis technique.³ Instead of using a spatula, the surgeon opens the flap with a Sinskey hook and uses forceps to peel it back. Careful irrigation of the bed is performed to reduce epithelial implantation. This technique has greatly reduced the number of post-enhancement ingrowth cases.

Management of epithelial ingrowth is often simply observation. Most cases are self-limiting because epithelial cells deprived of normal nutritional sources and environment fail to thrive and often undergo apoptosis. In persistent cases, surgical removal may be necessary. Bandage contact lenses are commonly used in these cases to help maintain closure of the interface and prevent recurrence of ingrowth.

References

1. Calvillo MP et al. Corneal reinnervation after LASIK: prospective 3-year longitudinal study. Invest Ophthalmol Vis Sci. 2004 Nov;45(11):3991-6.
2. Asano-Kato N. et al. Epithelial ingrowth after laser in situ keratomileusis: clinical features and possible mechanisms. Am J Ophthalmol. 2002 Dec;134(6):801-
3. Wilson SE., Santhiago MR. Flaporhexis: Rapid and effective technique to limit epithelial ingrowth after LASIK enhancement. J Cataract Refract Surg. 2012 Jan;38(1):2-4.