In vivo confocal laser microscopy of morphologic changes after small incision lenticule extraction with accelerated cross-linking (SMILE Xtra) in patients with thin corneas and high myopia.

Abstract

To evaluate the microstructural modifications and safety of small incision lenticule extraction combined with accelerated cross-linking (SMILE Xtra) in high myopia and thin corneas by means of in vivo confocal microscopy (IVCM) and 3D-OCT after a 6-month follow-up. Forty-three eyes with high myopia and thin corneas were enrolled. All eyes underwent SMILE procedure. After the lenticule was extracted, 0.25% riboflavin was injected into the interface and allowed to diffuse for 60s. The eye was irradiated with UVA radiation of 30mW/cm2 for 90s through the cap. The total energy delivered was 2.7J/cm2. Morphologic modifications of corneal architecture were evaluated prior to SMILE Xtra and 7days, 1, 3, and 6months after SMILE by in vivo confocal microscopy (IVCM) and 3D-OCT. The corneal epithelial cells showed slight damage until 3months postoperatively. The subepithelial nerve plexus decreased but no absence within the treatment zone at the first week after treatment, recolonized at 3months postoperatively, and had mostly recovered at the 6months postoperative but remained less than its normal baseline state. Keratocytes were absent in the surgical interface area, and the presence of strong reflective particles and cicatricial reaction in the anterior stroma were observed during the entire 6-month examination period. Increased hyperreflectivity was observed from the cap side at a depth of 60 µm to stroma bed at a depth of 388 µm through 6months. The depth of the demarcation line in 40 eyes (93.0%) was at a mean depth of 296.12±47.86μm (range, 211-388μm). No particular change between preoperative and postoperative corneal endothelium was observed. Confocal microscopy showed increased hyperreflectivity in the SMILE Xtra eyes, and no changes in corneal endothelium. We confirmed the safety of the SMILE Xtra but recognize that larger and longer-term studies of SMILE Xtra are necessary.