An interventional study of SMILE surgery with Visumax 500 and SMILE surgery with Visumax 800 in Myopia, sponsored by Singapore Eye Research Institute. Recruiting at 1 site in Singapore. Open to participants aged 21 Years and older. Per ClinicalTrials.gov, last updated 2026-04-01.
Sponsored by Singapore Eye Research Institute · Not applicable, Interventional, and Treatment
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.
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.
1,159 studies on the registry are indexed under Myopia; 225 are open to participants now.
This study's planned enrollment of 100 is above the median of 78 across 923 interventional studies indexed under Myopia.
Browse Myopia studies →Singapore Eye Research Institute is the lead sponsor of 27 studies on the registry; 12 are open to participants now.
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Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
A weakened immune system. It can come from an illness, such as HIV or some blood cancers, or from medicines that turn the immune system down, for example after an organ transplant or for an autoimmune disease; steroids at higher doses count.
Read whether the line is about a condition or about medicines, and which medicines and doses it means.
Corticosteroids (steroids)
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Immunosuppression
A weakened immune system. It can come from an illness, such as HIV or some blood cancers, or from medicines that turn the immune system down, for example after an organ transplant or for an autoimmune disease; steroids at higher doses count.
Read whether the line is about a condition or about medicines, and which medicines and doses it means.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Eyes that have undergone SMILE using Visumax 500 laser system
Procedure: SMILE surgery with Visumax 500
Eyes that have undergone SMILE using Visumax 800 laser system
Procedure: SMILE surgery with Visumax 800
Routinely conducted procedure using Visumax 500 laser system for correction of myopia.
Routinely conducted procedure using Visumax 800 laser system for correction of myopia.
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.
Time frame: 1 year
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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: 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).
Time frame: 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.
Time frame: 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).
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: From the start of surgery to 1 year post-procedure
Plan to share: No
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