Short-term and long-term effects of small incision lenticule extraction (SMILE) on corneal endothelial cells.

Purpose: Small incision lenticule extraction (SMILE) is being used increasingly as a novel approach to correct refractive errors with femtosecond laser. The study was aimed to investigate the corneal endothelial changes 1 day (short term) and 1 year (long term) after SMILE procedure.

Methods: In this prospective study, a total of 56 eyes of 30 patients with myopia ranging from -3.25 to -8.25 diopters (D) and cylinder up to -3.50D were treated by SMILE. Postoperative uncorrected distance visual acuity (UDVA) and complications were assessed. Endothelial cell density (ECD), the coefficient of variation (CV), and the percentage of hexagonal cells were measured using a noncontact specular microscope preoperatively and at 1 day and 1 year postoperatively. The estimated residual stromal thickness (RST) of each patient was recorded.

Results: The median UDVA improved significantly from 1.00logMAR preoperatively to -0.10logMAR both at 1 day and 1 year (p<0.001). No eyes developed corneal edema or other complications during the follow-up period. There were no significant changes in the ECD, CV or the percentage of hexagonal cells at any visit point (all p>0.05). The mean estimated RST was 355.1±32.2μm (range 290-429μm). Endothelial cell changes in terms of ECD, CV or the percentage of hexagonal cells were not correlated with the estimated RST (p>0.05).

Conclusions: SMILE yielded improvement in visual acuity and no adverse effects to corneal endothelial cells were found. However, further studies with a lower preoperative ECD and deeper lenticule extraction are needed to conduct.