VISULYZE-assisted nomogram optimization enhances astigmatism correction accuracy in keratorefractive lenticule...

Keratorefractive lenticule extraction (KLEx) commonly relies on empirical nomogram adjustments to improve refractive accuracy; however, astigmatism correction remains suboptimal. VISULYZE (Carl Zeiss Meditec AG) enables data-driven nomogram optimization, but its differential effectiveness across astigmatism severities has not been fully characterized. This study compared VISULYZE-assisted nomogram optimization with empirical nomogram adjustment for spherical and astigmatic correction, using stratified vector analysis to quantify gains in precision.

This retrospective case-control study included 206 eyes that underwent KLEx between December 2023 and July 2024 and completed a minimum 3-month follow-up. Eyes were assigned to either VISULYZE-assisted nomogram optimization (VISULYZE group, n = 99) or conventional empirical adjustment with a 10% spherical power increment (control group, n = 107). Stratified analyses were performed for low-to-moderate astigmatism (< 2.00 D; 57 vs. 62 eyes) and high astigmatism (≥2.00 D; 42 vs. 45 eyes). Primary outcomes included uncorrected distance visual acuity (UDVA), best-corrected distance visual acuity (BCVA), spherical equivalent (SE) accuracy, and residual astigmatism. Astigmatism vector analysis was performed using the Alpins method, including target-induced astigmatism (TIA), surgically induced astigmatism (SIA), difference vector (DV), and correction index (CI). Two-way analysis of variance was used to test interaction effects between nomogram type and astigmatism severity.

At 3 months, 100% of eyes in the VISULYZE group achieved a UDVA of 20/20 or better, compared with 98% of control eyes; furthermore, 87% of the VISULYZE group vs. 73% of the control group achieved 20/16 or better (P = 0.045). SE within ±0.50 D was achieved in 100% of VISULYZE eyes and 94.4% of control eyes (P = 0.017). Residual astigmatism of 0.50 D or less was observed in 99% vs. 93.5% of eyes, respectively (P = 0.042). Stratified analysis showed consistent benefits: both the low-to-moderate and high astigmatism subgroups demonstrated significantly better SE accuracy and lower residual astigmatism with VISULYZE (both P < 0.05). Interaction analysis (nomogram type × astigmatism severity) showed no significant effect on any primary outcome (all P > 0.05), indicating consistent VISULYZE-associated benefits across strata. Vector analysis showed significantly smaller DV values in VISULYZE eyes across both strata (0.00 vs. 0.25 D, P < 0.001; the TIA-SIA correlation was stronger in low-to-moderate astigmatism (R² = 0.9798 vs. 0.9363). Efficacy and safety indices did not differ significantly between groups.

VISULYZE-assisted nomogram optimization improved the accuracy of both spherical and astigmatic correction in KLEx, with consistent benefits across astigmatism severities. This data-driven, iterative refinement paradigm may standardize nomogram development and may be particularly valuable for less experienced surgeons transitioning from empirical adjustment to evidence-based, dynamically optimized surgical planning.