Comparison of Myopic Small Incision Lenticule Extraction (SMILE) With VISUMAX 500 Versus VISUMAX 800 Platforms

Surgical correction of refractive errors is widely performed. Small incision lenticule extraction (SMILE) is a flapless refractive procedure introduced in 2011 for the treatment of myopia and myopic astigmatism. In this procedure, a stromal lenticule is created within the cornea using a femtosecond laser and extracted through a small incision (2.0-5.0 mm). The procedure involves docking, femtosecond laser application, lenticule dissection from the surrounding stroma, and lenticule extraction. The VisuMax 800 femtosecond laser system has recently been introduced and incorporates several technical advancements compared with the previous VisuMax 500 platform, including a faster 2-MHz laser frequency, a centration guidance system (CentraLign), a cyclotorsion compensation system (OcuLign), separate laser and microscope arms, and heads-up docking. Early reports of SMILE performed using the VisuMax 800 have demonstrated excellent visual and refractive outcomes that appear comparable to those reported with the VisuMax 500 femtosecond laser. However, limited data are available directly comparing the two platforms across multiple clinical, biomechanical, molecular, and subjective outcome measures. This randomized controlled contralateral-eye study will enroll 100 patients undergoing bilateral SMILE surgery. In each participant, one eye will be randomly assigned to undergo SMILE using the VisuMax 500 platform and the fellow eye will undergo SMILE using the VisuMax 800 platform. This design allows direct within-patient comparison while minimizing inter-individual variability. The study aims to compare refractive and visual outcomes, corneal biomechanical changes, tear proteomic profiles, corneal lenticule metabolomic characteristics, ocular surface parameters, patient-reported subjective outcomes, and surgeons' intraoperative experiences between the two platforms. Assessments will be performed preoperatively (baseline), immediately after surgery, and at postoperative follow-up visits at 1 day, 1 week, 1 month, 3 months, 6 months, and 12 months.