Comparison of Effective Optical Zone, Lenticule Decentration, and Corneal Aberrations Following KLEx Extraction Between the VisuMax 800 and VisuMax 500

Purpose: To compare the effective optical zone (EOZ), extent of lenticule decentration, and corneal higher order aberrations (HOAs) after keratorefractive lenticule extraction (KLEx) using the VisuMax 800 and 500 (Carl Zeiss Meditec AG). Methods: This was a prospective, matched case–control study controlled for programmed sphere (PS: ±0.25 diopters [D]), cylinder (PC: ±0.25 D), and optical zone (±0.1 mm). The EOZ and decentration values were obtained from the tangential topography difference map. The refractive outcomes and corneal HOAs were compared between the two platforms at the 3-month postoperative visit. Results: A total of 95 right eyes of 95 patients who underwent KLEx using the VisuMax 800 and 95 patients using the VisuMax 500 were included. Both platforms are effective and safe for the treatment of myopia and astigmatism. No significant difference was found in the percentage reduction of EOZ between the two platforms (16.52 ± 4.53% vs 16.42 ± 4.60%, P = .637). Multiple linear regression revealed that, for both platforms, PS and mean keratometry were negatively correlated with the percentage reduction in EOZ, whereas PC was positively correlated with the percentage reduction in EOZ. The absolute values of the vertical decentration were significantly lower for the VisuMax 800 (0.14 ± 0.10 vs 0.21 ± 0.14 mm, P < .001). No significant differences in postoperative total HOAs, horizontal and vertical coma, or spherical aberration were found between the two platforms ( P > .05). Conclusions: Both platforms achieved good and comparable refractive, EOZ, and HOAs outcomes. The VisuMax 800 demonstrated higher centration accuracy.