Comparison of Two Rotational Alignment Methods for Astigmatism Correction in SMILE Surgery

NCT07696468 | Not Yet Recruiting

• 1 other identifier: IIT2026071
• Study Type: interventional
• Target: 52
• Locations: 1 country
• Sites: 1

Brief Summary

Small incision lenticule extraction (SMILE) is a commonly used corneal refractive procedure for correcting myopia and myopic astigmatism. During astigmatism correction, eye rotation between the upright examination position and the supine surgical position may affect the alignment of the astigmatic treatment axis and may contribute to residual astigmatism after surgery. Manual limbal marking is a commonly used method to guide cyclotorsion adjustment during refractive surgery. OcuLign is an assisted cyclotorsion control function of the VISUMAX 800 platform that helps identify ocular rotation and guide axis alignment during SMILE. However, direct clinical evidence comparing OcuLign-assisted cyclotorsion control with manual limbal marking during SMILE is limited. This study is a single-center, prospective, randomized, masked, contralateral-eye non-inferiority trial. Adults aged 18 to 40 years with stable myopia and astigmatism who plan to undergo bilateral SMILE surgery will be enrolled. In each participant, one eye will receive SMILE with OcuLign-assisted cyclotorsion control, and the fellow eye will receive SMILE with manual limbal marking-guided cyclotorsion adjustment. The treatment assigned to the right eye will be determined by randomization. The primary objective is to compare residual refractive astigmatism at 3 months after surgery between the two methods. Secondary outcomes include visual acuity, refractive predictability and stability, astigmatism vector analysis, higher-order aberrations, contrast sensitivity, patient-reported quality of vision, overall satisfaction, and safety outcomes. Participants will be followed for approximately 6 months after surgery.

Conditions

Myopia; Refractive Ametropia

Keywords

myopia; SMILE; VisuMax 800; Cyclotorsion

Outcome Measures

Primary Outcomes (1)

• Residual refractive astigmatism

  Residual refractive astigmatism will be measured as the absolute manifest cylinder power in diopters at 3 months after SMILE. The primary analysis will compare residual refractive astigmatism between eyes treated with OcuLign-assisted cyclotorsion control and eyes treated with manual limbal marking-guided cyclotorsion adjustment to evaluate non-inferiority.

  3 months after surgery

Secondary Outcomes (10)

• Astigmatic correction predictability

  1 month, 3 months, and 6 months after surgery

• Astigmatic Correction Assessed by Alpins Vector Analysis

  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)

OcuLign-Assisted Cyclotorsion Control

EXPERIMENTAL

One eye of each participant will undergo SMILE using OcuLign-assisted cyclotorsion control on the VISUMAX 800 platform. OcuLign will be used intraoperatively to assist in identifying ocular rotation and guiding astigmatic axis alignment. Apart from the cyclotorsion adjustment method, the surgical parameters, lenticule design, suction procedure, postoperative medication, and follow-up schedule will be the same as those used for the fellow eye.

Procedure: Device-assisted cyclotorsion control during SMILE

Manual Limbal Marking-Guided Adjustment

ACTIVE COMPARATOR

The fellow eye of each participant will undergo SMILE using manual limbal marking-guided cyclotorsion adjustment. Limbal reference marks will be made in the upright preoperative position, and intraoperative axis alignment will be manually adjusted according to the marks and the surgical reference direction. Apart from the cyclotorsion adjustment method, the surgical parameters, surgical procedure, postoperative medication, and follow-up schedule will be the same as those used for the contralateral eye.

Procedure: Manual limbal marking-guided cyclotorsion adjustment during SMILE

Interventions

Device-assisted cyclotorsion control during SMILE PROCEDURE

One eye of each participant will undergo SMILE using device-assisted cyclotorsion control with the OcuLign function of the VISUMAX 800 platform. During surgery, OcuLign will assist in identifying ocular rotation and guiding astigmatic axis alignment. Apart from the cyclotorsion adjustment method, the surgical parameters, lenticule design, suction procedure, postoperative medication, and follow-up schedule will be the same as those used for the fellow eye.

Also known as: OcuLign-assisted cyclotorsion control, VISUMAX 800 OcuLign

OcuLign-Assisted Cyclotorsion Control

Manual limbal marking-guided cyclotorsion adjustment during SMILE PROCEDURE

The fellow eye of each participant will undergo SMILE using manual limbal marking-guided cyclotorsion adjustment. Limbal reference marks will be made in the upright preoperative position, and intraoperative axis alignment will be manually adjusted according to the limbal marks and the surgical reference direction. Apart from the cyclotorsion adjustment method, the surgical parameters, surgical procedure, postoperative medication, and follow-up schedule will be the same as those used for the contralateral eye.

Manual Limbal Marking-Guided Adjustment

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 myopic astigmatism and stable refractive status for \>= 1 year.
• Normal corneal morphology in both eyes, with corneal thickness and other ocular parameters meeting the requirements for SMILE surgery.
• Preoperative corrected distance visual acuity (CDVA) \>= 1.0 in both eyes.
• Manifest refractive cylinder \>= 0.75 D in both eyes, with an interocular difference in absolute cylinder power \<= 1.00 D.
• Both eyes can provide reliable preoperative upright-position image information required for astigmatic axis recognition, and are judged by the investigator to meet the requirements for OcuLign cyclotorsion recognition and axis alignment on the VISUMAX 800 platform.
• Voluntary to undergo bilateral SMILE surgery on the VISUMAX 800 platform, understanding the random eye-assignment scheme and signing the informed consent form.

You may not qualify if:

• History of prior ocular surgery, significant ocular trauma, or presence of ocular diseases that may affect the safety of refractive surgery or the interpretation of study outcomes.
• Irregular astigmatism or poor repeatability of bilateral astigmatism measurements, making reliable astigmatic axis analysis impossible.
• Presence of strabismus, nystagmus, significant binocular vision abnormality, or any condition that may affect fixation or cooperation during examinations.
• Severe systemic diseases that may affect ocular healing or surgical safety.
• Females who are pregnant or lactating.
• Inability to complete the required postoperative follow-up visits or questionnaire assessments.

Sponsors & Collaborators

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

Study Sites (1)

Zhongshan Ophthalmic Center

Guangzhou, Guangdong, 510060, China

Location

Related Publications (3)

• Chen P, Ye Y, Yu N, Zhang X, He J, Zheng H, Wei H, Zhuang J, Yu K. Comparison of Small Incision Lenticule Extraction Surgery With and Without Cyclotorsion Error Correction for Patients With Astigmatism. Cornea. 2019 Jun;38(6):723-729. doi: 10.1097/ICO.0000000000001937.

  PMID: 30950894 BACKGROUND

• Wang B, Wang Y, Zhang J. Comparison of astigmatic correction with and without limbal marking during small-incision lenticule extraction. J Cataract Refract Surg. 2022 Aug 1;48(8):924-928. doi: 10.1097/j.jcrs.0000000000000889.

  PMID: 35067664 BACKGROUND

• Yang X, Liu Y, Xiao K, Song Q, Xu Y, Li J, Zhou Y. Effect of Cyclotorsion Compensation in Small Incision Lenticule Extraction Surgery for the Correction of Myopic Astigmatism: A Systematic Review and Meta-Analysis. Ophthalmol Ther. 2024 May;13(5):1271-1288. doi: 10.1007/s40123-024-00921-2. Epub 2024 Mar 18.

  PMID: 38498276 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: July 6, 2026
• First Posted: July 10, 2026
• Study Start: July 13, 2026
• Primary Completion (Estimated): June 30, 2027
• Study Completion (Estimated): June 30, 2027
• Last Updated: July 15, 2026

Record last verified: 2026-07

Data Sharing

• IPD Sharing: Will not share

Locations

CN (1)