Myopia, Refractive Ametropia
Conditions
Keywords
myopia, SMILE, Refractive Surgery, Randomized Clinical Trial, Angle Kappa, VisuMax 800
Brief summary
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
Detailed description
Angle kappa refers to the offset between the visual axis and the pupil center and may influence the centration of the treatment zone during corneal refractive surgery. Inaccurate centration can lead to decentered ablation and may affect postoperative visual quality, especially higher-order aberrations. With the development of femtosecond laser technology, more precise intraoperative alignment has become possible. Small incision lenticule extraction (SMILE) is a commonly used corneal refractive procedure with good safety and predictability. The VisuMax 800 system incorporates machine vision-assisted centration guidance, which allows intraoperative adjustment of the treatment center according to the relative position of the corneal vertex and the pupil center. This provides the possibility of performing intraoperative compensation based on the kappa-angle offset. Previous studies have mainly evaluated centration adjustment in eyes with relatively large kappa-angle offsets and suggested that compensation may improve postoperative optical quality. However, for patients with small offsets, the necessity of intraoperative compensation remains unclear, and prospective randomized clinical trials are limited. The purpose of this study is to compare the visual outcomes and optical quality after SMILE with or without intraoperative kappa-angle compensation in patients with small kappa-angle offsets. This study is a single-center, randomized, parallel-group clinical trial. Participants who are suitable for SMILE surgery and have a kappa-angle offset less than 0.2 mm will be enrolled and randomly assigned to receive SMILE with compensation or SMILE without compensation using the VisuMax 800 platform. All surgeries will be performed by experienced surgeons using standard SMILE procedures. Participants will undergo routine ophthalmic examinations before surgery and will be followed after surgery at scheduled visits. The main evaluation will assess postoperative visual quality and refractive outcomes. Additional assessments will include visual acuity, refractive accuracy, higher-order aberrations, contrast sensitivity, and safety outcomes.
Interventions
PROCEDUREApply compensation to the Kappa angle.
SMILE 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.
PROCEDUREApply no compensation to the Kappa angle
SMILE 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.
Sponsors
Zhongshan Ophthalmic Center, Sun Yat-sen University
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
TREATMENT
Masking
DOUBLE (Subject, Outcomes Assessor)
Eligibility
Sex/Gender
ALL
Age
18 Years to 40 Years
Healthy volunteers
No
Inclusion criteria
1. 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. 2. Normal corneal morphology and corneal thickness meeting surgical requirements. 3. Preoperative corrected distance visual acuity (CDVA) \>= 1.0. 4. Preoperative synthetic Kappa angle offset measured \>= 0.10 mm and \< 0.20 mm. 5. Voluntarily agree to undergo SMILE surgery on the VISUMAX 800 platform, understand the randomization scheme, and provide signed informed consent.
Exclusion criteria
1. History of prior ocular surgery, significant ocular trauma, or presence of corneal or ocular diseases that may affect the safety of refractive surgery. 2. Severe systemic diseases that may affect ocular healing or surgical safety. 3. Females who are pregnant or lactating. 4. Inability to cooperate as required to complete the procedure or follow-up visits.
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Coma aberration | 3 months after surgery | Coma aberration measured by wavefront aberrometry to evaluate the effect of intraoperative kappa-angle compensation on postoperative optical quality. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Higher-order aberrations | 1 month, 3 months, and 6 months after surgery | Total higher-order aberrations, spherical aberration, and trefoil aberration measured using wavefront aberrometry under standardized conditions to evaluate postoperative optical quality. |
| Optical zone decentration | 3 months after surgery | Decentration of the optical zone measured using corneal topography by determining the displacement between the optical zone center and the corneal vertex. |
| Visual acuity | 1 month, 3 months, and 6 months after surgery | Binocular uncorrected distance visual acuity and corrected distance visual acuity measured using standardized visual acuity charts to evaluate visual performance and safety. |
| Manifest refraction | 1 month, 3 months, and 6 months after surgery | Postoperative sphere, cylinder, and spherical equivalent measured by manifest refraction. |
| Refractive accuracy | 1 month, 3 months, and 6 months after surgery | Proportion of eyes within predefined ranges of target refraction to evaluate refractive predictability. |
| Refractive stability | 1 month to 6 months after surgery | Refractive stability will be assessed as the change in manifest spherical equivalent refraction between postoperative visits. |
| Contrast sensitivity | 3 months after surgery | Contrast sensitivity will be measured using a standardized contrast sensitivity testing system (CSV-1000, VectorVision, USA) at multiple spatial frequencies. |
| Quality of Vision (QoV) score | 3 months after surgery | Visual symptoms will be assessed using the Quality of Vision (QoV) questionnaire, which evaluates the frequency, severity, and bothersome nature of visual disturbances. Scores are recorded on ordinal scales, with higher scores indicating worse visual quality. |
| Patient satisfaction score | 3 months after surgery | Patient satisfaction will be assessed using a 5-point rating scale. Scores range from 1 to 5, with higher scores indicating greater satisfaction. |
| Adverse events | Up to 6 months after surgery | Incidence of intraoperative or postoperative complications, including loss of corrected distance visual acuity and other clinically significant events. |
Countries
China
Outcome results
None listed