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

• Conditions: Myopia
• Interventions: Procedure: Corneal lenticule extraction for advanced refractive correction (CLEAR)

• Registration Number: NCT04817592
• Lead Sponsor: University of Bern

Brief 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 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 Timeline

• Study First Submitted: 2021-03-15
• Study First Submitted QC: 2021-03-23
• Study First Posted: 2021-03-26
• Status Verified: 2021-04
• Last Update Submitted: 2021-09-29
• Last Update Posted: 2021-09-30
• Study Start: 2021-12-01
• Primary Completion: 2022-03-30
• Study Completion: 2022-03-30

Recruitment & Eligibility

• Status: UNKNOWN
• Sex: All
• Target Recruitment: 100

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 & Design

• Study Type: OBSERVATIONAL
• Study Design: Not specified

Arm && Interventions

Group	Intervention	Description
Age1(20-25)	Corneal lenticule extraction for advanced refractive correction (CLEAR)	The groups are divided as per age
Age3(30-35)	Corneal lenticule extraction for advanced refractive correction (CLEAR)	-
Age5(40-45)	Corneal lenticule extraction for advanced refractive correction (CLEAR)	-
Age2(25-30)	Corneal lenticule extraction for advanced refractive correction (CLEAR)	-
Age4(35-40)	Corneal lenticule extraction for advanced refractive correction (CLEAR)	-

Primary Outcome Measures

Name	Time	Method
Biomechanics of extracted lenticule	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.

Trial Locations

Locations (1)

IROC AG; 🇨🇭 Zurich, Switzerland