One-year outcomes of Q-value-guided FS-LASIK in patients with high versus low astigmatism: A prospective comparative study

Femtosecond laser-assisted in situ keratomileusis (FS-LASIK) is the preferred treatment for astigmatism, but high astigmatism (≥2.5 diopters, D) remains challenging due to increased corneal reshaping needs and higher-order aberrations (HOAs). Q-value-guided FS-LASIK optimizes corneal asphericity to improve outcomes, yet its efficacy in high astigmatism (HA) patients is understudied. To evaluate the 1-year visual, corneal biomechanical, and aberrometric outcomes of Q-value-guided FS-LASIK in HA vs low astigmatism (LA, ≤1.0 D) patients. This prospective study enrolled 120 patients (120 eyes) at Zhangjiakou Aier Eye Hospital (April 2021-May 2023), stratified into HA (n = 60 eyes, ≥2.5 D) and LA (n = 60 eyes, ≤1.0 D) groups. All patients underwent Q-value-guided FS-LASIK using WaveLight FS200 (flap creation) and EX500 (stromal ablation). Evaluations included uncorrected/corrected distance visual acuity, Pentacam HR (HOAs: spherical aberration, coma), Corvis ST II (biomechanics: stiffness parameter at first applanation, ambrosio relational thickness through the horizontal meridian, integrated inverse radius, 2 mm deformation amplitude ratio), and Alpins vector analysis (astigmatism correction) preoperatively and at 1, 3, 6, and 12 months postoperatively. At 12 months, 100% of patients in both groups achieved uncorrected distance visual acuity ≥ 20/20, with no corrected distance visual acuity decline. Safety (HA:1.06 ± 0.05; LA:1.04 ± 0.08) and efficacy (HA:1.11 ± 0.11; LA:1.08 ± 0.10) indices were comparable (P > .05). HA patients had a smaller optical zone (6.03 ± 0.26 vs 6.36 ± 0.23 mm, P < .0001) and higher 12-month HOAs (e.g., spherical aberration root mean square: 0.693 ± 0.053 vs 0.502 ± 0.042, P < .001). Postoperative biomechanical changes (decreased stiffness parameter at first applanation/ ambrosio relational thickness through the horizontal meridian, increased integrated inverse radius/2 mm deformation amplitude ratio) stabilized by 1 month with no between-group differences (P > .05). Vector analysis showed higher target-induced astigmatism (2.47 ± 0.57 vs 0.51 ± 0.18 D) and surgically induced astigmatism (2.62 ± 0.66 vs 0.52 ± 0.31 D) in HA (P < .001), with more HA eyes (65%) having angle of error within ± 5° versus LA (39%). Q-value-guided FS-LASIK is safe and effective for both HA and LA patients, with stable 1-year outcomes. While HA patients exhibit higher residual HOAs, optimizing surgical parameters (e.g., optical zone size) may mitigate this limitation.