Surface quality of human corneal lenticules after SMILE assessed using environmental scanning electron microscopy

To assess the cut quality of the anterior and posterior surfaces of intrastromal refractive lenticules removed during small incision lenticule extraction (SMILE).

The VisuMax femtosecond laser (500 kHz; Carl Zeiss Meditec, Dublin, CA) was used to perform SMILE on 8 eyes of 5 individuals to correct only myopia (no cylinder). The cut energy index was 26 (equivalent to an energy of 130 nJ) with a 2.5 × 2.5 μm spot/track separation. The lenticule diameter was 6.5 mm with a minimum edge thickness of 15 μm and the cap diameter was 7.3 mm with an intended thickness of 120 μm. After laser treatment, the lenticule was loosened with a spatula and removed with forceps. The extracted lenticules were placed in 2% formalin and sent for imaging with an environmental scanning electron microscope. Images of the anterior and posterior surfaces of the lenticules were obtained at multiple magnifications (100×, 250×, and 500×). Surface quality was evaluated by an investigator who specializes in electron microscopy using three criteria: overall surface regularity, percent of surface irregularity, and position of irregular area.

Both the anterior and posterior surfaces of the extracted lenticules were smooth and absent of surface irregularities. The cut edges also appeared uniform. Jagged edges were seen in several images, but were clearly caused by the forceps during extraction.

Using the VisuMax laser to perform SMILE produces smooth cuts absent of surface irregularities.