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

NCT07512102 | Recruiting

• 1 other identifier: IIT2025193
• Study Type: interventional
• Target: 100
• Locations: 1 country
• Sites: 1

Brief 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

Keywords

myopia; SMILE; Refractive Surgery; Randomized Clinical Trial; Angle Kappa; VisuMax 800

Outcome Measures

Primary Outcomes (1)

• Coma aberration

  Coma aberration measured by wavefront aberrometry to evaluate the effect of intraoperative kappa-angle compensation on postoperative optical quality.

  3 months after surgery

Secondary Outcomes (10)

• Higher-order aberrations

  1 month, 3 months, and 6 months after surgery

• Optical zone decentration

  3 months after surgery

• Visual Acuity

  1 month, 3 months, and 6 months after surgery

• Manifest refraction

  1 month, 3 months, and 6 months after surgery

• Refractive accuracy

  1 month, 3 months, and 6 months after surgery

Study Arms (2)

Low-Level compensation group

ACTIVE COMPARATOR

Subjects underwent SMILE surgery on the VisuMax 800 platform. Preoperatively, decentration coordinates (x, y) were measured. While preserving the directional sign, the absolute value of the planned compensation was set to 50% of the measured decentration; the values were then rounded to the nearest increment permitted by the device input precision and entered into the system. All other surgical procedures, as well as postoperative medication and follow-up protocols, were performed according to a standardized regimen.

Procedure: Apply low compensation to the Kappa angle.

High-Level compensation group

EXPERIMENTAL

Subjects also underwent SMILE surgery on the VisuMax 800 platform. Decentration coordinates (x, y) were measured, and the theoretical compensation was set at 100% of the measured decentration. While preserving the directional sign, the measured values were entered directly into the device without any additional adjustment. Except for the different compensation strategy, all other surgical procedures and postoperative management were identical to those of the low-compensation group.

Procedure: Apply high compensation to the Kappa angle.

Interventions

Apply high compensation to the Kappa angle. PROCEDURE

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.

High-Level compensation group

Apply low compensation to the Kappa angle. PROCEDURE

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.

Low-Level compensation group

Eligibility Criteria

• Age: 18 Years - 40 Years
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64)

You may qualify if:

• 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.
• Voluntary to undergo SMILE surgery on the VISUMAX800 platform, understanding the random grouping scheme and signing the informed consent form.

You may not qualify if:

• 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.

Sponsors & Collaborators

• Zhongshan Ophthalmic Center, Sun Yat-sen University: lead

Study Sites (1)

Zhongshan Ophthalmic Center

Guangzhou, Guangdong, 510060, China

RECRUITING

Related Publications (7)

• Doostparast A, Ghandhari M, Rastegar M, Khosronejad AH, Ghandhari M, Eslampoor A. Distribution and inter-device agreement of chord mu/alpha lengths and axes between Pentacam HR, Sirius, and IOLMaster 700. Photodiagnosis Photodyn Ther. 2025 Dec;56:105275. doi: 10.1016/j.pdpdt.2025.105275. Epub 2025 Nov 6.

  PMID: 41205666 BACKGROUND

• Shao T, Wang Y, Ng ALK, Chan TCY, Hao W, Zhang J, Cheng GPM, Jhanji V. The Effect of Intraoperative Angle Kappa Adjustment on Higher-Order Aberrations Before and After Small Incision Lenticule Extraction. Cornea. 2020 May;39(5):609-614. doi: 10.1097/ICO.0000000000002274.

  PMID: 32040010 BACKGROUND

• Lai X, Liu X, Zeng T, Huang Y, Yang X. Comparison of visual outcomes and optical aberrations after SMILE with intraoperative Kappa angle adjustments between small and large Kappa angles. Sci Rep. 2024 Jun 24;14(1):14551. doi: 10.1038/s41598-024-65366-w.

  PMID: 38914606 BACKGROUND

• Deng M, Zhou D, Li M, Shi Y, Sun L, Zou J, Ma X. Evaluation of corneal asymmetry and higher-order aberrations after small incision lenticule extraction for moderate and high myopia. Int Ophthalmol. 2025 Jun 1;45(1):218. doi: 10.1007/s10792-025-03576-5.

  PMID: 40451982 BACKGROUND

• Vingopoulos F, Zisimopoulos A, Kanellopoulos AJ. Comparison of effective corneal refractive centration to the visual axis: LASIK vs SMILE, a contralateral eye digitized comparison of the postoperative result. J Cataract Refract Surg. 2021 Dec 1;47(12):1511-1518. doi: 10.1097/j.jcrs.0000000000000687.

  PMID: 34074993 BACKGROUND

• McAlinden C, Pesudovs K, Moore JE. The development of an instrument to measure quality of vision: the Quality of Vision (QoV) questionnaire. Invest Ophthalmol Vis Sci. 2010 Nov;51(11):5537-45. doi: 10.1167/iovs.10-5341. Epub 2010 May 26.

  PMID: 20505205 BACKGROUND

• Chang JS, Law AK, Ng JC, Chan VK. Comparison of refractive and visual outcomes with centration points 80% and 100% from pupil center toward the coaxially sighted corneal light reflex. J Cataract Refract Surg. 2016 Mar;42(3):412-9. doi: 10.1016/j.jcrs.2015.09.030.

  PMID: 27063522 BACKGROUND

MeSH Terms

Conditions

Myopia

Condition Hierarchy (Ancestors)

Refractive Errors; Eye Diseases

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: DOUBLE
• Who Masked: PARTICIPANT, OUTCOMES ASSESSOR
• Purpose: TREATMENT
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: March 21, 2026
• First Posted: April 6, 2026
• Study Start: April 8, 2026
• Primary Completion (Estimated): May 30, 2027
• Study Completion (Estimated): May 30, 2027
• Last Updated: July 7, 2026

Record last verified: 2026-03

Data Sharing

• IPD Sharing: Will not share

Locations

CN (1)