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

13 juli 2026 bijgewerkt door: Zhongshan Ophthalmic Center, Sun Yat-sen University

Comparison of Astigmatic Correction Outcomes Following SMILE With OcuLign-Assisted Cyclotorsion Control and Manual Limbal Marking: A Prospective Randomized Contralateral-Eye Noninferiority Study

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.

Studie Overzicht

Toestand

Nog niet aan het werven

Conditie

Interventie / Behandeling

Gedetailleerde beschrijving

Accurate alignment of the astigmatic treatment axis is an important factor in the correction of myopic astigmatism during small incision lenticule extraction (SMILE). Cyclotorsion may occur when a patient changes from the upright preoperative examination position to the supine surgical position, and may also be influenced by fixation, head position, and suction during surgery. Inadequate compensation for ocular rotation may reduce astigmatic correction accuracy and contribute to postoperative residual astigmatism.

Manual limbal marking is a commonly used method for cyclotorsion adjustment in corneal refractive surgery. This method is clinically feasible and widely used, but it depends on preoperative marking and intraoperative manual judgment. Marking clarity, ocular surface conditions, patient cooperation, and surgeon experience may affect the accuracy and reproducibility of the adjustment. OcuLign is an assisted cyclotorsion control function of the VISUMAX 800 platform that helps identify ocular rotation and guide axis alignment during SMILE. This study is designed to compare OcuLign-assisted cyclotorsion control with manual limbal marking-guided cyclotorsion adjustment during SMILE.

This trial uses a prospective, randomized, contralateral-eye non-inferiority design. Each participant will undergo bilateral SMILE surgery. One eye will be assigned to OcuLign-assisted cyclotorsion control, and the fellow eye will be assigned to manual limbal marking-guided cyclotorsion adjustment, according to a prespecified randomization sequence. This paired-eye design is intended to reduce inter-individual variability in refractive characteristics, healing response, and subjective visual perception. Apart from the method of cyclotorsion adjustment, surgical parameters, lenticule design, suction procedure, postoperative medication, and follow-up schedule will be kept consistent between the two eyes.

Participants and postoperative outcome assessors will be masked to the eye-level treatment assignment whenever feasible. The operating surgeon cannot be masked because the assigned cyclotorsion adjustment method must be performed during surgery. Postoperative assessments will be conducted at predefined follow-up visits through approximately 6 months after surgery.

The primary comparison will evaluate whether OcuLign-assisted cyclotorsion control is non-inferior to manual limbal marking-guided adjustment in terms of residual refractive astigmatism at 3 months after surgery. Secondary assessments will evaluate visual acuity, refractive predictability and stability, astigmatism vector parameters, higher-order aberrations, contrast sensitivity, patient-reported quality of vision, satisfaction, and safety. Safety monitoring will include loss of corrected distance visual acuity and postoperative adverse events.

Studietype

Ingrijpend

Inschrijving (Geschat)

52

Fase

  • Niet toepasbaar

Contacten en locaties

In dit gedeelte vindt u de contactgegevens van degenen die het onderzoek uitvoeren en informatie over waar dit onderzoek wordt uitgevoerd.

Studie Locaties

  • China
    • Guangdong
      • Guangzhou, Guangdong, China, 510060
        • Zhongshan Ophthalmic Center

Deelname Criteria

Onderzoekers zoeken naar mensen die aan een bepaalde beschrijving voldoen, de zogenaamde geschiktheidscriteria. Enkele voorbeelden van deze criteria zijn iemands algemene gezondheidstoestand of eerdere behandelingen.

Geschiktheidscriteria

Leeftijden die in aanmerking komen voor studie

  • Volwassen

Accepteert gezonde vrijwilligers

Nee

Beschrijving

Inclusion Criteria:

  1. Age range: 18 - 40 years old. Patients with myopic astigmatism and stable refractive status for >= 1 year.
  2. Normal corneal morphology in both eyes, with corneal thickness and other ocular parameters meeting the requirements for SMILE surgery.
  3. Preoperative corrected distance visual acuity (CDVA) >= 1.0 in both eyes.
  4. Manifest refractive cylinder >= 0.75 D in both eyes, with an interocular difference in absolute cylinder power <= 1.00 D.
  5. 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.
  6. Voluntary to undergo bilateral SMILE surgery on the VISUMAX 800 platform, understanding the random eye-assignment scheme and signing the informed consent form.

Exclusion Criteria:

  1. 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.
  2. Irregular astigmatism or poor repeatability of bilateral astigmatism measurements, making reliable astigmatic axis analysis impossible.
  3. Presence of strabismus, nystagmus, significant binocular vision abnormality, or any condition that may affect fixation or cooperation during examinations.
  4. Severe systemic diseases that may affect ocular healing or surgical safety.
  5. Females who are pregnant or lactating.
  6. Inability to complete the required postoperative follow-up visits or questionnaire assessments.

Studie plan

Dit gedeelte bevat details van het studieplan, inclusief hoe de studie is opgezet en wat de studie meet.

Hoe is de studie opgezet?

Ontwerpdetails

  • Primair doel: Behandeling
  • Toewijzing: Gerandomiseerd
  • Interventioneel model: Parallelle opdracht
  • Masker: Dubbele

Wapens en interventies

Deelnemersgroep / Arm
Interventie / Behandeling
Experimenteel: OcuLign-Assisted Cyclotorsion Control
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
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.
Andere namen:
  • OcuLign-assisted cyclotorsion control
  • VISUMAX 800 OcuLign
Actieve vergelijker: Manual Limbal Marking-Guided Adjustment
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
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.

Wat meet het onderzoek?

Primaire uitkomstmaten

Uitkomstmaat
Maatregel Beschrijving
Tijdsspanne
Residual refractive astigmatism
Tijdsspanne: 3 months after surgery
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

Secundaire uitkomstmaten

Uitkomstmaat
Maatregel Beschrijving
Tijdsspanne
Astigmatic correction predictability
Tijdsspanne: 1 month, 3 months, and 6 months after surgery
Astigmatic correction predictability will be assessed as the proportion of eyes with postoperative residual manifest cylinder within predefined thresholds, including ≤0.25 D, ≤0.50 D, and ≤1.00 D.
1 month, 3 months, and 6 months after surgery
Visual acuity
Tijdsspanne: 1 month, 3 months, and 6 months after surgery
Uncorrected distance visual acuity and corrected distance visual acuity will be measured using standardized visual acuity charts and recorded as logMAR visual acuity. Visual acuity-derived performance will also be summarized using the safety index and efficacy index, calculated from the same visual acuity measurements. The safety index is defined as postoperative corrected distance visual acuity divided by preoperative corrected distance visual acuity, and the efficacy index is defined as postoperative uncorrected distance visual acuity divided by preoperative corrected distance visual acuity.
1 month, 3 months, and 6 months after surgery
Manifest refraction
Tijdsspanne: 1 month, 3 months, and 6 months after surgery
Postoperative manifest refraction will include sphere, cylinder, and spherical equivalent measured by standard manifest refraction.
1 month, 3 months, and 6 months after surgery
Refractive accuracy
Tijdsspanne: 1 month, 3 months, and 6 months after surgery
Refractive accuracy will be assessed as the proportion of eyes with postoperative spherical equivalent within predefined ranges of the target refraction, including within ±0.25 D, ±0.50 D, and ±1.00 D.
1 month, 3 months, and 6 months after surgery
Refractive stability
Tijdsspanne: 1 month to 6 months after surgery
Refractive stability will be assessed as the change in manifest spherical equivalent refraction between postoperative follow-up visits.
1 month to 6 months after surgery
Contrast sensitivity
Tijdsspanne: 3 months after surgery
Contrast sensitivity will be measured under standardized conditions using the CSV-1000 contrast sensitivity testing system at multiple spatial frequencies, including 3, 6, 12, and 18 cycles per degree. The area under the log contrast sensitivity function may be calculated as a summary measure when appropriate.
3 months after surgery
Quality of Vision score
Tijdsspanne: 3 months after surgery
Subjective visual symptoms will be assessed using the Quality of Vision questionnaire, which evaluates the frequency, severity, and bothersome nature of visual disturbances such as glare, halos, and double vision. Higher scores indicate worse subjective visual quality.
3 months after surgery
Overall visual satisfaction score
Tijdsspanne: 3 months after surgery
Overall visual satisfaction will be assessed using a 5-point Likert rating scale. Scores range from 1 to 5, with higher scores indicating greater satisfaction.
3 months after surgery
Astigmatic Correction Assessed by Alpins Vector Analysis
Tijdsspanne: 3 months after surgery
Postoperative astigmatic correction will be assessed using the Alpins vector analysis method based on refractive cylinder and axis data. This outcome will be used to describe the overall accuracy of astigmatism correction after surgery.
3 months after surgery
Higher-Order Wavefront Aberration Assessment
Tijdsspanne: 1 month, 3 months, and 6 months after surgery
Higher-order wavefront aberrations will be measured using wavefront aberrometry under standardized conditions to assess postoperative optical quality.
1 month, 3 months, and 6 months after surgery

Medewerkers en onderzoekers

Hier vindt u mensen en organisaties die betrokken zijn bij dit onderzoek.

Sponsor

Zhongshan Ophthalmic Center, Sun Yat-sen University

Publicaties en nuttige links

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Algemene publicaties

Studie record data

Deze datums volgen de voortgang van het onderzoeksdossier en de samenvatting van de ingediende resultaten bij ClinicalTrials.gov. Studieverslagen en gerapporteerde resultaten worden beoordeeld door de National Library of Medicine (NLM) om er zeker van te zijn dat ze voldoen aan specifieke kwaliteitscontrolenormen voordat ze op de openbare website worden geplaatst.

Bestudeer belangrijke data

Studie start (Geschat)

13 juli 2026

Primaire voltooiing (Geschat)

30 juni 2027

Studie voltooiing (Geschat)

30 juni 2027

Studieregistratiedata

Eerst ingediend

6 juli 2026

Eerst ingediend dat voldeed aan de QC-criteria

6 juli 2026

Eerst geplaatst (Werkelijk)

10 juli 2026

Updates van studierecords

Laatste update geplaatst (Werkelijk)

15 juli 2026

Laatste update ingediend die voldeed aan QC-criteria

13 juli 2026

Laatst geverifieerd

1 juli 2026

Meer informatie

Termen gerelateerd aan deze studie

Trefwoorden

Aanvullende relevante MeSH-voorwaarden

Andere studie-ID-nummers

  • IIT2026071

Plan Individuele Deelnemersgegevens (IPD)

Bent u van plan om gegevens van individuele deelnemers (IPD) te delen?

NEE

Informatie over medicijnen en apparaten, studiedocumenten

Bestudeert een door de Amerikaanse FDA gereguleerd geneesmiddel

Nee

Bestudeert een door de Amerikaanse FDA gereguleerd apparaatproduct

Nee

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