Comparison of Myopic Small Incision Lenticule Extraction (SMILE) With VISUMAX 500 Versus VISUMAX 800 Platforms

Small incision lenticule extraction (SMILE) procedure is a well-known procedure for the correction of myopia. The purpose of this research study is to compare the two SMILE procedures with different laser platforms (VISUMAX 500 and VISUMAX 800) used for the correction of short-sightedness. The VISUMAX 800 and VISUMAX 500 perform the same procedure, but the VISUMAX 800 is a newer platform. This study is being done to see if the newer VISUMAX 800 provides the same or better results than the VISUMAX 500.

Study Overview

• Status: Recruiting
• Conditions: Myopia
• Intervention / Treatment: Procedure: SMILE surgery with Visumax 500; Procedure: SMILE surgery with Visumax 800

Detailed Description

Surgical correction of refractive errors is widely performed. Small incision lenticule extraction (SMILE) is a flapless refractive procedure introduced in 2011 for the treatment of myopia and myopic astigmatism. In this procedure, a stromal lenticule is created within the cornea using a femtosecond laser and extracted through a small incision (2.0-5.0 mm). The procedure involves docking, femtosecond laser application, lenticule dissection from the surrounding stroma, and lenticule extraction.

The VisuMax 800 femtosecond laser system has recently been introduced and incorporates several technical advancements compared with the previous VisuMax 500 platform, including a faster 2-MHz laser frequency, a centration guidance system (CentraLign), a cyclotorsion compensation system (OcuLign), separate laser and microscope arms, and heads-up docking. Early reports of SMILE performed using the VisuMax 800 have demonstrated excellent visual and refractive outcomes that appear comparable to those reported with the VisuMax 500 femtosecond laser. However, limited data are available directly comparing the two platforms across multiple clinical, biomechanical, molecular, and subjective outcome measures.

This randomized controlled contralateral-eye study will enroll 100 patients undergoing bilateral SMILE surgery. In each participant, one eye will be randomly assigned to undergo SMILE using the VisuMax 500 platform and the fellow eye will undergo SMILE using the VisuMax 800 platform. This design allows direct within-patient comparison while minimizing inter-individual variability.

The study aims to compare refractive and visual outcomes, corneal biomechanical changes, tear proteomic profiles, corneal lenticule metabolomic characteristics, ocular surface parameters, patient-reported subjective outcomes, and surgeons' intraoperative experiences between the two platforms.

Assessments will be performed preoperatively (baseline), immediately after surgery, and at postoperative follow-up visits at 1 day, 1 week, 1 month, 3 months, 6 months, and 12 months.

• Study Type: Interventional
• Enrollment (Estimated): 100
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Jodhbir S Mehta, MD, FRCS; Phone Number: +65 6322 7478; Email: jodhbir.s.mehta@singhealth.com.sg

Study Locations

• Singapore
  • Singapore, Singapore, 169856
    • Recruiting
    • Singapore National Eye Centre (SNEC)
    • Contact: Jodhbir S Mehta, MD, FRCS; Phone Number: +65 6322 7478; Email: jodhbir.s.mehta@singhealth.com.sg

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Cycloplegic spherical equivalent of >-1.00D
• Refractive cylinder -2.00 D or less; anisometropia <1.00D
• Best spectacle corrected visual acuity (BSCVA) of 6/12 or better in both eyes
• Spherical or cylindrical error has progressed at -0.50 D or less per year from date of baseline measurement in both eyes
• Contact lens wearers must have removed contact lenses at least 2 weeks before the baseline measurement
• No evidence of irregular astigmatism on corneal topography in both eyes

Exclusion Criteria:

• Progressive or unstable myopia and/or astigmatism
• Clinical or corneal topographic evidence of keratoconus
• Residual, recurrent or active ocular disease such as uveitis, severe dry eyes, severe allergic eye disease, glaucoma, visually significant cataract, and retinal disease
• Previous corneal surgery or trauma within the corneal flap zone
• Patent corneal vascularization within 1 mm of the corneal flap zone
• Taking systemic medications likely to affect wound healing, such as corticosteroids and antimetabolites
• Systemically immunocompromised or systemic disease likely to affect wound healing, such as diabetes, connective tissue disease, and severe atopy; pregnant or nursing

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Double

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: Eyes that have undergone SMILE with Visumax 500; Eyes that have undergone SMILE using Visumax 500 laser system	Procedure: SMILE surgery with Visumax 500; Routinely conducted procedure using Visumax 500 laser system for correction of myopia.
Active Comparator: Eyes that have undergone SMILE with Visumax 800; Eyes that have undergone SMILE using Visumax 800 laser system	Procedure: SMILE surgery with Visumax 800; Routinely conducted procedure using Visumax 800 laser system for correction of myopia.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Visual outcomes	Best-corrected visual acuity (BCVA), Uncorrected visual acuity (UCVA). Refractive outcomes: Nine standard graphs for corneal refractive surgery: Post-operative UDVA versus pre-operative CDVA; Change in Snellen lines from pre-operative CDVA to post-operative UDVA; Change in Snellen lines from pre-operative CDVA to post-operative CDVA; Attempted versus achieved spherical equivalent refraction; Accuracy of post-operative spherical equivalent refraction to target; Stability of spherical equivalent refraction, shown as the trend of mean Spherical Equivalent (SE) at preop, one week, one month, three months, six months, and one year post-operatively; Change in refractive astigmatism; Target-induced astigmatism (TIA) vs. surgically induced astigmatism (SIA); Histogram of refractive astigmatism angle of error. Refractive predictability, which is defined as the proportion number of eyes achieving a postoperative spherical equivalent (SE) within ±1.0 D of the intended target.	1 year

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Patient-reported intraoperative experiences	The in-house patient questionnaire is used to assess patient-reported subjective intraoperative experiences. Rather than utilizing numerical scoring, it uses qualitative descriptors and binary "Yes/No" responses to evaluate perceived discomfort, fear levels, and visual phenomena-such as light perception loss or image clarity-during specific surgical steps like vacuum suction and lenticule creation. The form also includes a ranking system for identifying the most fearful parts of the procedure and asks patients to compare the experience, including perceived speed, between their right and left eyes.	Up to 1 hour post-surgery
Patient-reported outcomes	The in-house questionnaire is used to assess patient-reported outcomes. This evaluates postoperative outcomes for SMILE surgery performed on the VisuMax 500 and 800 platforms. Rather than using simple numerical scores, the assessment captures subjective patient experiences through qualitative descriptors and frequency-based scales for symptoms like light sensitivity, dryness, and visual disturbances. It also identifies specific environmental triggers, such as lighting conditions, and monitors the functional impact of surgery on daily activities like night driving.	1 year
Surgeon experience	The Surgeon Questionnaire evaluates the intraoperative technical performance and early postoperative outcomes of SMILE procedures. Rather than relying on a single numerical score, it utilizes a combination of binary "Yes/No" indicators for surgical complications and descriptive scales to grade tissue adherence and ease of lenticule extraction.	Up to 1 hour post-surgery
Ocular Surface Disease Index (OSDI)	The Ocular Surface Disease Index (OSDI) is a 12-item questionnaire used to assess the symptoms of ocular irritation. The score ranges from 0 to 100. Higher scores indicate more severe ocular surface disease and a worse outcome.	1 year
Ocular Pain Assessment Survey (OPAS)	The Ocular Pain Assessment Survey (OPAS) is a questionnaire used to evaluate ocular pain and its impact on daily functioning and quality of life. The score ranges from 0 to10, where 0 indicates no pain or interference and 10 indicates the most severe pain or maximum interference.	1 year
Corvis ST	The Corvis ST (Corneal Visualization Scheimpflug Technology) is a non-contact device that measures corneal biomechanical properties by recording corneal deformation in response to an air puff. The higher deformation amplitude (mm) indicating softer cornea and lower corneal stiffness.	1 year
BOSS scan	The Brillouin Optical Scanning System (BOSS) is a non-contact device that maps corneal and ocular tissue biomechanics using Brillouin light scattering. It measures Brillouin frequency shifts at multiple points, which are converted to stiffness values (GPa). Higher Brillouin shifts indicate stiffer tissue, while lower shifts indicate softer tissue, allowing quantitative assessment of corneal biomechanical properties.	1 year
Schirmer I test	The Schirmer test is a clinical measure of tear production. A standardized filter paper strip is placed in the lower conjunctival fornix for 5 minutes, and the length of wetting (mm) is recorded. Lower values indicate reduced tear secretion, with ≤5 mm typically suggesting severe aqueous tear deficiency, 6-10 mm moderate, and >10 mm normal tear production.	1 year
Tear Break-Up Time (TBUT)	Tear Break-Up Time (TBUT) measures tear film stability by timing the interval between a blink and the first appearance of a dry spot on the cornea after fluorescein instillation. It is recorded in seconds, with shorter times indicating less stable tear film. Values <10 s are generally considered abnormal, while longer times indicate normal tear stability.	1 year
Corneal sensitivity	Corneal sensitivity is measured using a Cochet-Bonnet esthesiometer, which applies a 0-6 cm nylon filament to different corneal locations. The filament length at which an escape response, blink reflex, or subject-reported sensation occurred is recorded. Summing the responses across all tested locations yielded a total corneal sensitivity score ranging from 0 to 30 cm, with higher values indicating greater corneal sensitivity.	1 year
Corneal and Conjunctival Fluorescein Staining (NEI score)	The National Eye Institute (NEI) scale is used to grade the severity of ocular surface staining. The cornea is divided into 5 sectors (central, superior, inferior, nasal, and temporal), and the conjunctiva is divided into 6 sectors. Each sector is scored from 0 to 3 based on the density of staining. The total corneal score ranges from 0 to 15, and the total conjunctival score ranges from 0 to 18 (total maximum score of 33). A score of 0 represents no staining (best outcome), and a higher total score indicates more severe ocular surface damage (worst outcome).	1 year
Oxford Grading Scale for ocular surface staining	The Oxford Grading Scale is a validated method used to quantify the severity of epithelial damage via fluorescein staining. Staining is assessed in three zones: the nasal conjunctiva, the cornea, and the temporal conjunctiva. Each zone is graded from 0 to 5 based on the density of punctate staining. The total score ranges from 0 to 15, where a score of 0 indicates no staining (best outcome) and a score of 15 indicates confluent staining (worst outcome). Higher scores represent increased ocular surface disease severity.	1 year
Corneal Tomography	Corneal tomography is a non-invasive imaging technique that generates a comprehensive 3D map of the cornea's front and back surfaces. The measurements include corneal thickness (μm) and surface curvature (D).	1 year
Anterior segment optical coherence tomography (ASOCT)	Anterior Segment Optical Coherence Tomography (ASOCT) is a non-invasive imaging technique that produces high-resolution, cross-sectional views of the front portion of the eye. It provides precise structural measurements, including corneal thickness (µm) and anterior chamber dimensions or curvature (mm). These detailed values allow for the clear visualization of ocular anatomy and the monitoring of subtle changes in tissue structure over time.	1 year
Higher order abberations (HOAs)	Higher-order aberrations (HOAs) are complex optical imperfections, such as coma and spherical aberration, that cannot be corrected by standard spectacles or contact lenses. These irregularities are measured using wavefront sensing technology, which quantifies the deviation of light as it passes through the eye's optical media. The primary numerical result is the Root Mean Square (RMS) error, expressed in microns (μm), which represents the total magnitude of these distortions. In a typical healthy eye, the HOA RMS is generally less than 0.30 μm, while values exceeding 0.50 μm often indicate clinically significant visual disturbances like halos or glare.	Change in HOAs from Baseline to 12 months
In-vivo confocal microscopy (IVCM)	In Vivo Confocal Microscopy (IVCM) is a non-invasive imaging technique that provides high-resolution, real-time "optical sections" of the living cornea at a cellular level. Rather than traditional photography, it produces detailed scans of individual corneal layers, allowing for the precise measurement of cell density in cells/mm² and nerve fiber morphology in µm/mm². Particularly this is used to assess the nerve and keratocyte changes after surgery.	Change in IVCM findings from Baseline to 12 months
Intraoperative centration of the laser	Intraoperative centration of the laser is measured by the offset distance (in millimeters) between the intended treatment center and the actual center of the laser-cut lenticule. During docking, the surgeon aligns the suction cone with a specific reference point, such as the corneal vertex or pupil center, while the patient fixes their gaze. An offset of less than 0.2 mm indicates ideal centration, whereas a displacement above 0.5 mm is generally considered clinically significant and may cause visual disturbances.	During the surgical procedure
Complications	Incidence of surgical and clinical complications related to the SMILE procedure is recorded. Intraoperative complications include suction loss, opaque bubble layer formation, or difficult lenticule extraction. Postoperative complications include epithelial ingrowth, diffuse lamellar keratitis, infectious keratitis, or transient light sensitivity syndrome. Complications will be recorded based on clinical examination and slit-lamp microscopy. Results will be reported as the number of eyes experiencing one or more adverse events.	From the start of surgery to 1 year post-procedure

Collaborators and Investigators

• Sponsor: Singapore Eye Research Institute
• Investigators: Principal Investigator: Jodhbir S Mehta, MD, FRCS, Singapore National Eye Centre

Study record dates

Study Major Dates

• Study Start (Actual): December 1, 2025
• Primary Completion (Estimated): May 1, 2027
• Study Completion (Estimated): June 1, 2027

Study Registration Dates

• First Submitted: March 16, 2026
• First Submitted That Met QC Criteria: March 26, 2026
• First Posted (Actual): April 1, 2026

Study Record Updates

• Last Update Posted (Actual): April 1, 2026
• Last Update Submitted That Met QC Criteria: March 26, 2026
• Last Verified: March 1, 2026

More Information

Terms related to this study

• Keywords: RCT; SMILE; Refractive surgery; Visumax
• Additional Relevant MeSH Terms: Eye Diseases; Refractive Errors; Myopia
• Other Study ID Numbers: 2024-4584

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: Yes