Epithelial Ingrowth After SMILE Eye Surgery

One uncommon complication with lasik is something known as epithelial ingrowth. This occurs when the surface layer of the cornea, called epithelium, makes its way underneath the lasik flap and starts growing. The procedural design of SMILE eye surgery, however, makes this very difficult to occur.

During lasik, a large flap is created on the cornea. There is a large break within the epithelium to create this flap. If the flap edge does not seal perfectly or if it disturbed during the healing process, the epithelial cells can migrate underneath the flap and start growing. Modern femtosecond laser created flaps have significantly reduced this potential due to their side-cut design, but because there is a large circumferential break in the epithelium there is still that risk.

SMILE instead only has a small incision through the epithelium. If we look at just the amount of break through the epithelium, SMILE has much less than lasik and so naturally it makes sense that epithelial ingrowth is much less common with SMILE.

Additionally, SMILE preserves the position of the anterior cap of cornea. Unlike a flap, it is much easier for the edge of the incision to seal up well and not be disturbed when there is no potential of a lateral shift in corneal tissue. The incision with SMILE remains lined up to prevent any gap for the epithelium to make its way into the SMILE interface.

These anatomical differences with SMILE make epithelial ingrowth highly unusual.