The goal of this clinical trial is to compare two intraoperative kappa-angle compensation strategies during small incision lenticule extraction (SMILE) using the VisuMax 800 platform in patients with relatively large kappa-angle offsets.
Angle kappa represents the difference between the visual axis and the pupil center. In patients with a large offset, pupil-centered treatment may lead to decentration of the optical zone, which can induce higher-order aberrations and affect postoperative visual quality. The VisuMax 800 system allows intraoperative adjustment of the treatment center based on the measured offset, making different compensation strategies possible.
The main questions this study aims to answer are:
Does low kappa-angle compensation (50%) result in lower postoperative higher-order aberrations than high compensation (100%)? Does the compensation strategy influence visual acuity, refractive outcomes, contrast sensitivity, and subjective visual quality after SMILE? Are the measurements obtained from different diagnostic devices consistent when evaluating kappa-related parameters?
Researchers will compare SMILE with low compensation to SMILE with high compensation to determine which strategy provides better optical quality and visual performance.
Participants will:
Undergo SMILE surgery using either low or high kappa-angle compensation Complete scheduled postoperative examinations at 1 month, 3 months, and 6 months Receive measurements of visual acuity, refraction, higher-order aberrations, contrast sensitivity, and patient-reported visual outcomes Be monitored for safety outcomes and adverse events during follow-up
Age range: 18 - 40 years old. Patients with stable refractive status for >= 1 year, having myopia or myopic astigmatism, with refractive power within the range of SMILE procedure.
Normal corneal morphology and corneal thickness meeting the surgical requirements.
Best corrected visual acuity (CDVA) before surgery >= 1.0.
The kappa angle-related offset coordinates (x, y) obtained before surgery, with the absolute value of either |x| or |yl| of any eye >= 0.20mm.
History of prior ocular surgery, significant ocular trauma, or presence of corneal or ocular diseases that may affect the safety of refractive surgery.
Severe systemic diseases that may affect ocular healing or surgical safety.
Females who are pregnant or lactating.
Inability to cooperate as required to complete the procedure or follow-up visits.