New mechanism for epithelial ingrowth after small incision lenticule extraction: Vertical epithelial gas breakthrough.

A 41-year-old man underwent SMall Incision Lenticule Extraction (SMILE) to treat myopia in both eyes. The femtosecond procedure was uneventful but a paracentral epithelial blister appeared during the dissection of the anterior plane of the lenticule in the right eye. The posterior surface of the lenticule was dissected without any complication. The surgery of the left eye was uneventful. In the postoperative period, he developed a paracentral epithelial ingrowth in his right eye, exactly underneath the site where the epithelial blister had been noted during the dissection of the lenticule. This induced irregular astigmatism, severely affecting his visual acuity. The decision of surgical treatment was made. After the de-epithelialization of an area of 6mm around the ingrowth, the SMILE incision was opened, and the epithelial ingrowth was dissected and removed from the interface. One month later, uncorrected visual acuity was 20/20, no epithelial ingrowth was observed at the interface, and only the edge of the former ingrowth was barely visible in slit lamp examination. No recurrence was observed. We hypothesize that a vertical epithelial gas breakthrough created a fistula between the interface and the epithelium, forming a pathway for the epithelial cells and giving rise to epithelial ingrowth.