Surface quality of human corneal SMILE lenticules in comparison with microkeratome free caps

Abstract

Purpose The aim of this study was to compare electron microscopic morphological images of the posterior surface of corneal lenticules removed during femtosecond laser small-incision lenticule extraction (SMILE) with free corneal caps created using a mechanical microkeratome. Design An in-vitro comparative study was carried out including 30 human corneal lenticules from 15 patients who underwent bilateral SMILE refractive procedure (SMILE group) using the 500 kHz VisuMax femtosecond laser and 20 cadaveric donor corneas that were cut creating free caps using the Moria M2 microkeratome. Setting The present study was carried out at Roayah Vision Correction Center and Faculty of Science, Alexandria University. Participants and methods A total of 15 SMILE lenticules and 15 microkeratome free caps were examined by scanning electron microscopy (SEM), and another 15 SMILE lenticules and five microkeratome free caps were examined by transmission electron microscopy. The JEOL JSM-5300LV SEM was used for observations. A new scoring system was used for comparison. Results The surface and edge of SMILE lenticules showed more roughness in the form of tissue bridges, dome-shaped elevations, more cavitational changes, and tiny tissue fragments compared with the undersurface of free corneal microkeratome caps, but the difference was not statistically significant on SEM (P=0.40654). Conclusion SMILE induces corneal surface roughness and structural changes that are slightly more pronounced than those induced by the microkeratome. The observed changes may cause surgically induced optical aberrations. Energy settings still need further adjustment to be able to create reproducible, predictable smooth surfaces in lenticules of SMILE cases.

Keywords

• electron microscopy
• microkeratome
• small-incision lenticule extraction