Comparison of Refractive Outcomes Between Small Lenticule Extraction Using a 500 KHz and a 2 MHz Femtosecond Laser

Area of Science:

• Ophthalmology
• Refractive Surgery
• Biomedical Engineering

Background:

• Small incision lenticule extraction (SMILE) is a prevalent refractive surgery technique.
• Comparing different laser platforms is crucial for optimizing surgical outcomes.
• Evaluating the efficacy of VisuMax 500 versus VisuMax 800 in myopia and astigmatism correction is warranted.

Purpose of the Study:

• To compare the efficacy of myopia and myopic astigmatism correction between VisuMax 500 and VisuMax 800 SMILE surgery.
• To assess visual acuity, refractive error, and astigmatism axis correction accuracy between the two laser platforms.

Main Methods:

• A retrospective case-control study involving 249 patients (493 eyes) with VisuMax 500 and 85 patients (169 eyes) with VisuMax 800.
• Patients underwent SMILE surgery using the VisuMax 500 nomogram.
• Outcomes including uncorrected distance visual acuity (UDVA), residual refractive error, and astigmatism angle of error were analyzed at 2 months post-operation.

Main Results:

• Both VisuMax 500 and VisuMax 800 achieved high rates of postoperative UDVA of 20/20 (99% and 97%, respectively).
• VisuMax 800 demonstrated significantly lower residual myopia (-0.09 ± 0.50 CD vs. -0.21 ± 0.49 CD; p=0.005).
• VisuMax 800 showed superior astigmatism correction accuracy, with 84% of eyes within ±15° of the intended meridian versus 71% for VisuMax 500 (p=0.002), and a smaller mean absolute angle of error (8.3° vs. 14.1°; p<0.001).

Conclusions:

• Both VisuMax 500 and VisuMax 800 are effective for myopia correction via SMILE surgery.
• VisuMax 800 offers enhanced precision for astigmatism axis correction compared to VisuMax 500.
• Potential bias due to evaluating platforms from the same manufacturer is a limitation.