Comparison of Low- Versus High-Level Angle Kappa Compensation Strategies in SMILE Using the VisuMax 800: A Randomized Clinical Trial

Summary

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

Conditions

• Myopia
• Refractive Ametropia

Interventions

PROCEDURE

Apply high 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. It 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 high-level compensation group, a high level of compensation for the kappa angle was applied during the preoperative parameter input.

PROCEDURE

Apply low 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. It is essentially an all-femtosecond corneal refractive procedure. Its basic principle is to use a femtosecond laser to create a lenticule within the corneal stroma and a small incision, and then remove the lenticule through the incision, thereby reshaping the corneal curvature to correct myopia and astigmatism. In the low-level compensation group, a low level of kappa-angle compensation was applied during the preoperative parameter input.

Sponsors & Collaborators

• Zhongshan Ophthalmic Center, Sun Yat-sen University

  lead OTHER

Study Design

Allocation

RANDOMIZED

Purpose

TREATMENT

Masking

DOUBLE

Model

PARALLEL

Eligibility

Min Age

18 Years

Max Age

40 Years

Sex

ALL

Healthy Volunteers

No

Timeline & Regulatory

Start

2026-04-08

Primary Completion

2027-05-30

Completion

2027-05-30

Countries

• China

Study Locations