MyopiaCLEAR BiomechNCT04817592
Characterization of the Corneal Biomechanics of Patients Treated by Corneal Lenticule Extraction for Advanced Refractive Correction (CLEAR) to Correct Myopia
An observational study of Myopia, run by University of Bern at 1 site in Switzerland.
Trial summary
This study aims to perform biomechanical tests on extracted CLEAR lenticles that are routinely discarded after surgery. The investigators also aim to perform Brillouin microscopy to get an in-vivo assessment of the patient's cornea preoperatively and to correlate this data with the postoperative characterization of… Read more about this study
- Who is it for?
- Ages 20 to 50 yearsHealthy volunteers can take part
- Conditions the study is for
- Myopia
- What is being tested?
- Corneal lenticule extraction for advanced refractive correction (CLEAR)
- Type of treatment
- Surgery or procedure
- How many people
- 100 participants
- Where
- 1 siteSwitzerland
- Study dates
- 1 Jun 2026to 31 Dec 2027
- Phase
- Observational
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 20 to 50 years
- All sexes
- Healthy volunteers accepted
- Adult
Study population: Healthy subjects voluntarily undergoing routinely prescribed CLEAR /SMILE intervention
Who may be able to join
- Patients scheduled for CLEAR procedures for myopia (range: >-3D with an astigmatism <0.25D) in the age group 20-50 years.
- Willing and able to return for scheduled follow-up examinations
- Able to provide written informed consent and follow study instructions in English or German
Who cannot join
- Irregular corneal topo-/tomography (Asymmetry >1.0D within the inner 5mm)
- Previous intraocular or corneal surgery of any kind in the eye to be treated, including any type of surgery for either refractive or therapeutic purposes.
- History of steroid-responsive rise in intraocular pressure, glaucoma, or preoperative intraocular pressure (IOP) > 21 mmHg in either eye.
- History of diabetes, diagnosed autoimmune disease, connective tissue disease or clinically significant atopic syndrome.
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
Switzerland1 site
IROC AG
Zurich, 8002
Theo Seiler, Priv.-Doz. Dr. med., theo@seiler.tv
About this study
This study aims to perform biomechanical tests on extracted CLEAR lenticles that are routinely discarded after surgery. The investigators also aim to perform Brillouin microscopy to get an in-vivo assessment of the patient's cornea preoperatively and to correlate this data with the postoperative characterization of the extracted corneal lenticule. The characterization will be done with established biomechanical and morphologic tests.
Read the detailed description
Refractive surgery techniques such as laser in situ keratomileusis (LASIK), corneal lenticule extraction (SMILE/CLEAR) and photorefractive keratectomy (PRK) are becoming increasingly popular among myopic patients. With current surgical planning tools, there is a reported 10-15 % chance of over/under correction, in particular with higher corrections. The biggest factor that leads to this discrepancy is the "one size fits all" approach. Patient specific characteristics of the eye such as the corneal material properties, are not considered in the surgical planning. This information is also essential for diagnosis and treatment of pathologies like keratoconus. New diagnostics devices based on e. g. Brillouin scattering are now introduced on the market, with the aim to provide an in-vivo quantification of the biomechanical tissue properties. However, the relationship between the Brillouin measurement and the biomechanical properties of the cornea is not fully understood yet. The investigators aim for determining an improved relationship between the optical Brillouin measurement performed in-vivo preoperatively and classical destructive biomechanical testing of the extracted corneal lenticule after the surgery. This lenticule is currently discarded after surgery.
The purpose of the study is to investigate the exact relationship between the classically determined material properties (by stress-/strain measurements) and optically obtained data by Brillouin scattering, which are collected during pre-op investigations. A precise characterization and relation between both measurements will allow clinicians to better predict surgical parameters and perform better refractive interventions. This information will also inform clinicians on the mechanical status of the cornea of patients suffering from subclinical keratoconus.
- Conditions
- Myopia
- Being tested
- Corneal lenticule extraction for advanced refractive correction (CLEAR)
- Keywords
- Cornea, SMILE, CLEAR
- Medical subject headings
- Myopia, Corneal Diseases
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Corneal lenticule extraction for advanced refractive correction (CLEAR)Procedure or surgery
Also called SMILE
Routinely conducted procedure for correction of Myopia
| Study group | Role | What they receive |
|---|---|---|
| Age1(20-25) | The groups are divided as per age Receives: Procedure: Corneal lenticule extraction for advanced refractive correction (CLEAR) | |
| Age2(25-30) | Not described Receives: Procedure: Corneal lenticule extraction for advanced refractive correction (CLEAR) | |
| Age3(30-35) | Not described Receives: Procedure: Corneal lenticule extraction for advanced refractive correction (CLEAR) | |
| Age4(35-40) | Not described Receives: Procedure: Corneal lenticule extraction for advanced refractive correction (CLEAR) | |
| Age5(40-45) | Not described Receives: Procedure: Corneal lenticule extraction for advanced refractive correction (CLEAR) |
What is being measured
The primary outcome is the main question the study is designed to answer.
Biomechanics of extracted lenticule
During the CLEAR intervention, the lenticule extracted will be marked for physiological direction to identify the nasal-temporal and superior-inferior directions and stored at room temperature in normal culture medium from eye banking with 6% dextran. The mechanical experiments on these lenticules, will be performed within 24hours after extraction to preserve the sample properties. The samples will undergo uniaxial tensile testing in IROC using the UStretch (Cellscale, Waterloo, ON, Canada) device. Post tensile testing, the samples will be imaged using Second-harmonic imaging microscopy (SHG microscopy). SHG microscopy will be used to determine the in-plane probability distribution describing the orientation and density of the collagen fibrils present in the CLEAR lenticules. This information will be incorporated into a computational model which will simulate the uniaxial stress-strain measurements to further help us identify the parameters of a non-linear constitutive material model.
Measured: 1 year
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted26 Mar 2021
- Study start1 Jun 2026 (estimated)
- Primary completion1 Jun 2027 (estimated)
- Study completion31 Dec 2027 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for MyopiaStudies of the same condition, open and under way.
- More trials run by University of BernThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Observational
- Observational model
- Cohort
- Time perspective
- Prospective
- Enrolment
- 100 participants (estimated)
Sponsor and investigators
- Lead sponsor
- University of Bern
- Sponsor type
- University, hospital or other
- Responsible party
- Sponsor
- Investigators
- Philippe Büchler, Prof. Dr., Principal investigator, University of Bern
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT04817592
- Sponsor's protocol ID
- Basec Nr 2021-001-45
- Acronym
- CLEAR Biomech
- Status last verified
- Sep 2025
- First submitted
- 15 Mar 2021
- Last updated
- 19 Sep 2025
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 19 Sep 2025. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Characterization of the Corneal Biomechanics of Patients Treated by Corneal Lenticule Extraction for Advanced Refractive Correction (CLEAR) to Correct Myopia
- ClinicalTrials.gov ID
- NCT04817592
- Acronym / sponsor ID
- CLEAR Biomech / Basec Nr 2021-001-45
- Conditions
- Myopia
- Keywords
- Cornea, SMILE, CLEAR
- Study type
- Observational
- Recruitment status
- Not yet recruiting
- Enrolment
- 100 participants (estimated)
- Lead sponsor
- University of BernUniversity, hospital or other
- Study start
- 1 Jun 2026 (estimated)
- Primary completion
- 1 Jun 2027 (estimated)
- Study completion
- 31 Dec 2027 (estimated)
- First posted
- 26 Mar 2021 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
This study aims to perform biomechanical tests on extracted CLEAR lenticles that are routinely discarded after surgery. The investigators also aim to perform Brillouin microscopy to get an in-vivo assessment of the patient's cornea preoperatively and to correlate this data with the postoperative characterization of the extracted corneal lenticule. The characterization will be done with established biomechanical and morphologic tests.
Detailed description
Refractive surgery techniques such as laser in situ keratomileusis (LASIK), corneal lenticule extraction (SMILE/CLEAR) and photorefractive keratectomy (PRK) are becoming increasingly popular among myopic patients. With current surgical planning tools, there is a reported 10-15 % chance of over/under correction, in particular with higher corrections. The biggest factor that leads to this discrepancy is the "one size fits all" approach. Patient specific characteristics of the eye such as the corneal material properties, are not considered in the surgical planning. This information is also essential for diagnosis and treatment of pathologies like keratoconus. New diagnostics devices based on e. g. Brillouin scattering are now introduced on the market, with the aim to provide an in-vivo quantification of the biomechanical tissue properties. However, the relationship between the Brillouin measurement and the biomechanical properties of the cornea is not fully understood yet. The investigators aim for determining an improved relationship between the optical Brillouin measurement performed in-vivo preoperatively and classical destructive biomechanical testing of the extracted corneal lenticule after the surgery. This lenticule is currently discarded after surgery.
The purpose of the study is to investigate the exact relationship between the classically determined material properties (by stress-/strain measurements) and optically obtained data by Brillouin scattering, which are collected during pre-op investigations. A precise characterization and relation between both measurements will allow clinicians to better predict surgical parameters and perform better refractive interventions. This information will also inform clinicians on the mechanical status of the cornea of patients suffering from subclinical keratoconus.
Study design
- Observational model
- Cohort
- Time perspective
- Prospective
- Number of arms
- 5
| Arm | Type | Receives |
|---|---|---|
| Age1(20-25) | – | Procedure: Corneal lenticule extraction for advanced refractive correction (CLEAR)The groups are divided as per age |
| Age2(25-30) | – | Procedure: Corneal lenticule extraction for advanced refractive correction (CLEAR) |
| Age3(30-35) | – | Procedure: Corneal lenticule extraction for advanced refractive correction (CLEAR) |
| Age4(35-40) | – | Procedure: Corneal lenticule extraction for advanced refractive correction (CLEAR) |
| Age5(40-45) | – | Procedure: Corneal lenticule extraction for advanced refractive correction (CLEAR) |
Who may qualify
- Ages
- 20 to 50 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult
- Study population
- Healthy subjects voluntarily undergoing routinely prescribed CLEAR /SMILE intervention
Key inclusion criteria (3 listed)
- Patients scheduled for CLEAR procedures for myopia (range: >-3D with an astigmatism <0.25D) in the age group 20-50 years.
- Willing and able to return for scheduled follow-up examinations
- Able to provide written informed consent and follow study instructions in English or German
Key exclusion criteria (4 listed)
- Irregular corneal topo-/tomography (Asymmetry >1.0D within the inner 5mm)
- Previous intraocular or corneal surgery of any kind in the eye to be treated, including any type of surgery for either refractive or therapeutic purposes.
- History of steroid-responsive rise in intraocular pressure, glaucoma, or preoperative intraocular pressure (IOP) > 21 mmHg in either eye.
- History of diabetes, diagnosed autoimmune disease, connective tissue disease or clinically significant atopic syndrome.
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Corneal lenticule extraction for advanced refractive correction (CLEAR)Also: SMILERoutinely conducted procedure for correction of Myopia | Procedure or surgery | Age1(20-25), Age2(25-30), Age3(30-35), Age4(35-40), Age5(40-45) |
Primary outcome
Biomechanics of extracted lenticule
Time frame: 1 year
During the CLEAR intervention, the lenticule extracted will be marked for physiological direction to identify the nasal-temporal and superior-inferior directions and stored at room temperature in normal culture medium from eye banking with 6% dextran. The mechanical experiments on these lenticules, will be performed within 24hours after extraction to preserve the sample properties. The samples will undergo uniaxial tensile testing in IROC using the UStretch (Cellscale, Waterloo, ON, Canada) device. Post tensile testing, the samples will be imaged using Second-harmonic imaging microscopy (SHG microscopy). SHG microscopy will be used to determine the in-plane probability distribution describing the orientation and density of the collagen fibrils present in the CLEAR lenticules. This information will be incorporated into a computational model which will simulate the uniaxial stress-strain measurements to further help us identify the parameters of a non-linear constitutive material model.
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 19 Sep 2025.
- Individual participant dataSharing planned: No
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
Philippe Büchler, Prof. Dr. principal investigator
University of Bern
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
An observational study of Myopia, run by University of Bern at 1 site in Switzerland.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 3 inclusion and 4 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: opening soon, as of the sponsor's last update on 19 Sep 2025. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in Switzerland. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Philippe Büchler, Prof. Dr. (+41 31 684 14 10, philippe.buechler@unibe.ch), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Biomechanics of extracted lenticule (time frame: 1 year). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 19 Sep 2025; AzTrials last refreshed its copy on 8 Nov 2026.