Characterization of the Corneal Biomechanics of Patients Treated by Corneal Lenticule Extraction for Advanced Refractive Correction (CLEAR) to Correct Myopia (CLEAR Biomech)

September 18, 2025 updated by: University of Bern
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.

Study Overview

Status

Not yet recruiting

Conditions

Intervention / Treatment

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 Type

Observational

Enrollment (Estimated)

100

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Locations

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

20 years to 50 years (Adult)

Accepts Healthy Volunteers

Yes

Sampling Method

Non-Probability Sample

Study Population

Healthy subjects voluntarily undergoing routinely prescribed CLEAR /SMILE intervention

Description

Inclusion Criteria:

  • 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

Exclusion Criteria:

  • 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.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Observational Models: Cohort
  • Time Perspectives: Prospective

Cohorts and Interventions

Group / Cohort
Intervention / Treatment
Age1(20-25)
The groups are divided as per age
Procedure: Corneal lenticule extraction for advanced refractive correction (CLEAR)
Routinely conducted procedure for correction of Myopia
Other Names:
  • SMILE
Age2(25-30)
Procedure: Corneal lenticule extraction for advanced refractive correction (CLEAR)
Routinely conducted procedure for correction of Myopia
Other Names:
  • SMILE
Age3(30-35)
Procedure: Corneal lenticule extraction for advanced refractive correction (CLEAR)
Routinely conducted procedure for correction of Myopia
Other Names:
  • SMILE
Age4(35-40)
Procedure: Corneal lenticule extraction for advanced refractive correction (CLEAR)
Routinely conducted procedure for correction of Myopia
Other Names:
  • SMILE
Age5(40-45)
Procedure: Corneal lenticule extraction for advanced refractive correction (CLEAR)
Routinely conducted procedure for correction of Myopia
Other Names:
  • SMILE

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
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.
1 year

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

University of Bern

Investigators

  • Principal Investigator: Philippe Büchler, Prof. Dr., University of Bern

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Estimated)

June 1, 2026

Primary Completion (Estimated)

June 1, 2027

Study Completion (Estimated)

December 31, 2027

Study Registration Dates

First Submitted

March 15, 2021

First Submitted That Met QC Criteria

March 23, 2021

First Posted (Actual)

March 26, 2021

Study Record Updates

Last Update Posted (Estimated)

September 19, 2025

Last Update Submitted That Met QC Criteria

September 18, 2025

Last Verified

September 1, 2025

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • Basec Nr 2021-001-45

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

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

Clinical Trials on Myopia

Clinical Trials on Corneal lenticule extraction for advanced refractive correction (CLEAR)

Search Similar Trials

Sponsors and Collaborators

Medical Conditions

Drug Interventions

CROs by country

CROs in Bulgaria

Conditions

Rare Diseases

Drug Interventions

Dietary Supplements

Sponsor/Collaborators

Locations

Subscribe