The Impact of 'A Miss Is as Good as a Mile': Is Compensation Necessary for Minimal Ocular Deviation in Myopic Laser Surgery?

NCT07512115 | Recruiting

• 1 other identifier: IIT2025199
• Study Type: interventional
• Target: 224
• Locations: 1 country
• Sites: 1

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

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)

Non-compensation group

ACTIVE COMPARATOR

Subjects underwent SMILE surgery on the VisuMax 800 platform. Preoperative offset coordinates (x, y) were measured; however, while preserving the directional sign, no kappa-angle-based laser centration compensation was applied intraoperatively, and the treatment center was set according to the system's default centration method. Except for the difference in compensation strategy, all other surgical procedures and postoperative management were identical to those in the compensation group.

Procedure: Apply no compensation to the Kappa angle

Compensation group

EXPERIMENTAL

Subjects underwent SMILE surgery on the VisuMax 800 platform. Preoperative offset coordinates (x, y) were measured, and, while preserving the directional sign, a fixed intraoperative laser centration compensation of 0.1 mm was uniformly applied to all eligible study eyes to achieve a quantitative adjustment of the treatment center toward the visual axis. Except for the difference in compensation strategy, all other surgical procedures and postoperative management were identical to those in the non-compensation group.

Procedure: Apply compensation to the Kappa angle.

Interventions

Apply 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 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.

Compensation group

Apply no 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 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.

Non-compensation group

Eligibility Criteria

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

You may qualify if:

• 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.
• Voluntarily agree to undergo SMILE surgery on the VISUMAX 800 platform, understand the randomization scheme, and provide signed informed consent.

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: 2026-07

Data Sharing

• IPD Sharing: Will not share

Locations

CN (1)