Effects of femtosecond laser small incision lenticule extraction on corneal endothelial cells

AIM: To observe the changes of corneal endothelial cell density and morphology after femtosecond laser small incision lenticule extraction(SMILE). <p>METHODS: In this prospective study, 60 patients(120 eyes)with myopia or myopic astigmatism, who volunteered to receive SMILE from April 2014 to October 2014 in Shengjing Hospital of China Medical University, were divided into two groups: contact lens group(60 eyes)and non-contact lens group(60 eyes). The values of corneal endothelial cell density and the percentages of hexagonal cells, detected by NIDEK confoscan4 corneal confocal microscopy before and 1wk, 1, 6mo after surgery, were recorded and analyzed.<p>RESULTS: All patients were with successful surgery and there were no complications intraoperative and postoperative. No differences were noted between two groups in terms of average age, refractive error, stromal ablation depth, residual stromal bed depth, and postoperative uncorrected visual acuity(<i>P</i>>0.05). Using the analysis of variance of repeated measurement data, there were no statistically significant differences regarding mean endothelial cell density and percentage of hexagonal cells in pre- and 1wk, 1, 6mo post-SMILE within non-contact lens group(<i>F</i>=0.864, 2.488; <i>P</i>=0.460, 0.061). In the contact lens group, no differences were found regarding mean endothelial cell density in pre- and 1wk, 1, 6mo post-operation(<i>F</i>=0.135, <i>P</i>=0.939), but there were significant differences in the percentage of hexagonal cells(<i>F</i>=4.913, <i>P=</i>0.002). The percentage of hexagonal cells decreased significantly at 1wk post-operation(30.70±4.08)% compared with preoperative(32.23±4.15)%(<i>P</i>=0.045), returned to the preoperative levels at 1mo after surgery(33.05±4.28)%(<i>P</i>=0.364), and showed no difference(<i>P</i>=0.091)at 6mo after surgery(34.06±5.11)% with preoperative data. The percentages of hexagonal cells in the contact lens group were significantly lower in pre- and 1wk, 1mo post-operation than those in the non-contact lens group(<i>t</i>=2.051, 1.723, 2.092; <i>P</i>=0.037, 0.042, 0.034), however, there was no statistically significant difference between two groups at 6mo after surgery(<i>t</i>=0.131, <i>P</i>=0.986). <p>CONCLUSION: If the required residual stromal thickness limit was ≥300μm, SMILE to correct myopia or myopic astigmatism has no effect on the corneal endothelial cell density, only has short effect on the percentage of corneal hexagonal cells, which is slighter than wearing contact lens. SMILE to correct myopia is safe for corneal endothelium