The goal of this clinical trial is to evaluate the effect of intraoperative kappa-angle compensation on postoperative visual quality in patients undergoing small incision lenticule extraction (SMILE) using the VisuMax 800 platform. The study will enroll patients with myopia and a kappa-angle offset \< 0.2 mm.
The main questions it aims to answer are:
Does intraoperative kappa-angle compensation reduce postoperative higher-order aberrations after SMILE? Does kappa-angle compensation improve postoperative visual quality and refractive outcomes compared with no compensation?
Researchers will compare SMILE with intraoperative kappa-angle compensation to SMILE without compensation to determine whether compensation leads to better optical quality and visual performance.
Participants will:
Undergo SMILE surgery with or without intraoperative kappa-angle compensation Complete scheduled postoperative examinations at 1 week, 1 month, 3 months, and 6 months after surgery Receive measurements of visual acuity, refraction, higher-order aberrations, contrast sensitivity, and safety outcomes
Patients aged 18 to 40 years with myopia or myopic astigmatism and stable refraction for >=1 year, whose refractive errors fall within the treatable range of and meet the indications for SMILE surgery.
Normal corneal morphology and corneal thickness meeting surgical requirements.
Preoperative corrected distance visual acuity (CDVA) >= 1.0.
Preoperative synthetic Kappa angle offset measured >= 0.10 mm and < 0.20 mm.
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.
Parallel
Apply compensation to the Kappa angle.
Procedure/SurgerySMILE PRO is an upgraded version/procedural designation of SMILE (Small Incision Lenticule Extraction) performed on the ZEISS VisuMax 800 femtosecond laser platform and remains, in essence, an all-femtosecond corneal refractive procedure. Its basic principle is to use a femtosecond laser to create a lenticule within the corneal stroma together with a small incision, and then remove the lenticule through that incision, thereby reshaping the corneal curvature to correct myopia and astigmatism. In the compensation group, during preoperative parameter input, a fixed intraoperative laser centration compensation of 0.1 mm was uniformly applied to all study eyes meeting the inclusion criteria to achieve a quantitative adjustment of the treatment center toward the visual axis.
Apply no compensation to the Kappa angle
Procedure/SurgerySMILE PRO is an upgraded version/procedural designation of SMILE (Small Incision Lenticule Extraction) performed on the ZEISS VisuMax 800 femtosecond laser platform and remains, in essence, an all-femtosecond corneal refractive procedure. Its basic principle is to use a femtosecond laser to create a lenticule within the corneal stroma together with a small incision, and then remove the lenticule through that incision, thereby reshaping the corneal curvature to correct myopia and astigmatism. In the non-compensation group, no kappa-angle-based laser centration compensation was applied intraoperatively, and the treatment center was set according to the system's default centration method.
Coma aberration
Coma aberration measured by wavefront aberrometry to evaluate the effect of intraoperative kappa-angle compensation on postoperative optical quality.
Higher-order aberrations
Total higher-order aberrations, spherical aberration, and trefoil aberration measured using wavefront aberrometry under standardized conditions to evaluate postoperative optical quality.
Optical zone decentration
Decentration of the optical zone measured using corneal topography by determining the displacement between the optical zone center and the corneal vertex.
Visual acuity
Binocular uncorrected distance visual acuity and corrected distance visual acuity measured using standardized visual acuity charts to evaluate visual performance and safety.
Manifest refraction
Postoperative sphere, cylinder, and spherical equivalent measured by manifest refraction.
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