Comparison of Zeiss MEL90 and Alcon WaveLight EX500 Excimer Lasers in FDA Premarket Approval Trials for the Treatment of Myopia, Hyperopia, and Mixed Astigmatism

Abstract

Background/Objectives: Although both the MEL90 (Carl Zeiss Meditec AG, Jena, Germany) and WaveLight EX500 (Alcon Laboratories, Inc., Fort Worth, TX, USA) are two widely used excimer lasers, comparisons between the two remain limited. This study evaluates visual and refractive outcomes from the U.S. Food and Drug Administration (FDA) premarket approval trials of these platforms in the treatment of myopia with and without astigmatism, hyperopia with and without astigmatism, and mixed astigmatism. Methods: Clinical outcomes from FDA premarket approval trials were compared between the recently approved MEL90 and the WaveLight (now termed EX500) excimer lasers. Results: A total of 714 eyes (358 patients) from MEL90 and 1353 eyes (706 patients) from EX500 were analyzed up to 6 months postoperatively. In the hyperopia/hyperopic astigmatism cohort, the EX500 demonstrated greater efficacy relative to MEL90, with more eyes achieving a postoperative uncorrected distance visual acuity (UDVA) of 20/20 or better (48.6% vs. 68.7%, respectively; p < 0.001). In both the MEL90 and EX500, at least 85% of eyes with myopia/myopic astigmatism and 68% with mixed astigmatism achieved a postoperative UDVA of 20/20 or better. For all refractive cohorts, more than 95% of eyes achieved a UDVA of 20/40 or better at 6 months (all p > 0.05). The EX500 was more likely to demonstrate an improvement of more than two lines of UDVA compared to baseline CDVA (all p < 0.05). In contrast, the MEL90 showed greater predictability of spherical equivalent within ±0.50 D and ±1.00 D for the hyperopia/hyperopic astigmatism cohort (both p = 0.007), as well as within ±0.50 D for the myopia/myopic astigmatism cohort (p < 0.001). Postoperatively, both platforms were associated with decreased glare and halos, although findings were variable in the EX500 mixed astigmatism cohort. Conclusions: Both excimer lasers demonstrated safe and effective outcomes that exceed the threshold set by the FDA.

Keywords: EX500; LASIK; MEL90; WaveLight; excimer laser; predictability; refractive surgery; safety.

Figure 1

Comparison of uncorrected distance visual acuity (UDVA) between MEL90 and EX500 (A) myopia and myopic astigmatism, (B) hyperopia and hyperopic astigmatism, and (C) mixed astigmatism at 6 months. * Indicates statistically significant (p < 0.05).

Figure 2

Preoperative corrected distance visual acuity (CDVA) versus uncorrected distance visual acuity (UDVA) for the myopia cohort at 6 months. LogMAR values from the MEL90 studies were converted to Snellen equivalents for comparison. * Indicates statistically significant (p < 0.05).

Figure 3

Preoperative corrected distance visual acuity (CDVA) versus uncorrected distance visual acuity (UDVA) for the hyperopic cohort at 6 months. LogMAR values from the MEL90 studies were converted to Snellen equivalents for comparison. * Indicates statistically significant (p < 0.05).

Figure 4

Preoperative corrected distance visual acuity (CDVA) versus uncorrected distance visual acuity (UDVA) for the mixed astigmatism cohort at 6 months. LogMAR values from the MEL90 studies were converted to Snellen equivalents for comparison. * Indicates statistically significant (p < 0.05).

Figure 5

Accuracy of the manifest refraction spherical equivalent (MRSE) to the intended target for (A) myopia and myopic astigmatism, (B) hyperopia and hyperopic astigmatism, and (C) mixed astigmatism. * Indicates statistically significant (p < 0.05).

Figure 6

Correction indices of MEL90 and EX500 for (A) myopia and myopic astigmatism, (B) hyperopia and hyperopic astigmatism, and (C) mixed astigmatism stratified by preoperative cylinder.