Zero-Programmed-Sphere Keratorefractive Lenticule Extraction: Visual, Refractive, Anterior-Keratometric, and...

Zero-programmed-sphere keratorefractive lenticule extraction (KLEx), also called cylinder-only KLEx, is an uncommon cylinder-dominated treatment pattern in which the planned spherical correction is 0.00 diopters (D). To our knowledge, no published outcome data characterize this pattern. To address this lack of data, we retrospectively identified all such cases from a prospectively maintained single-center refractive-surgery registry and reported visual, refractive, anterior-keratometric, and wavefront outcomes, using Alpins vector analysis.

This study is retrospective single-center, single-surgeon case series of consecutive eyes treated with the SCHWIND ATOS femtosecond laser (SCHWIND eye-tech-solutions GmbH, Kleinostheim, Germany) between August 2024 and March 2026 at a programmed sphere of 0.00 D. Cycloplegic refraction was 0.00 D sphere in all 74 eyes (cycloplegic-plano target). The data lock was 31 March 2026, and eyes treated within the 3 months preceding that date were classified as not yet eligible to be included in the study. Inter-eye dependence was assessed using generalized estimating equations (GEE), and refractive stability was studied using a linear mixed model. Corrected distance visual acuity (CDVA) was imputed as uncorrected distance visual acuity (UDVA) when UDVA ≥ 20/20 and CDVA was missing. Complete-case sensitivity was also reported. The full-cohort ideal-outcome convention was determined using the refractive Alpins metric with a nonzero-difference-vector (DV) sensitivity subgroup; a parallel anterior-keratometric Alpins was run on the paired-keratometry subset.

A total of 74 eyes had been treated with the SCHWIND ATOS platform. At data lock, 62 were eligible for the ≥ 3-month follow-up and 37 had completed refractive examinations (analyzed primary cohort; mean age 33 years; mean programmed cylinder - 2.96 ± 1.30 D). UDVA ≥ 20/20 and ≥ 20/25 was achieved in 75.7% (Wilson 59.9-86.6%) and 91.9% of eyes, respectively; 83.8% of eyes were within ± 0.50 D of plano spherical equivalent refraction (SEQ); and 73.0% of eyes had postoperative cylinder ≤ 0.50 D. In terms of the refractive Alpins (side-by-side), the full-cohort correction index (CI) was 1.04, and mean absolute angle of error (|AoE|) was 2.9° versus 5.2° in the nonzero-DV subgroup (n = 21). In the 25-eye paired-keratometry subset, anterior-keratometric Alpins gave a CI of 1.05 and |AoE| of 13.4°, with residual anterior-keratometric DV of 1.12 ± 0.45 D versus refractive DV of 0.44 ± 0.60 D. Among the nine eyes with UDVA < 20/20, four had directly measured postoperative CDVA and five were not eligible for the imputation rule; the paired safety analysis therefore included 32 eyes (28 imputed + 4 directly measured), with complete-case (n = 4) and imputation-based indices 0.98 and 1.25, respectively. The analyzed cohort overrepresented against-the-rule (ATR) and oblique astigmatism (p = 0.002), so axis-fidelity estimates may reflect a more challenging case mix than the full treated population.

Zero-programmed-sphere KLEx produced favorable refractive outcomes in eyes reaching the ≥ 3-month endpoint. The 37/62 completion rate among eligible eyes and the imputation-based safety index limit generalizability. Wavefront changes were exploratory and generally followed the pattern expected after KLEx. The anterior-keratometric and refractive Alpins results diverged substantially, suggesting that future studies should include total corneal vector analysis and direct assessment of intraoperative rotation.