Assessment of Corneal Stiffness in Keratoconus After Crosslinking by Corvis ST and OCT.
NCT ID: NCT05161052
Last Updated: 2021-12-16
Study Results
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Basic Information
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UNKNOWN
NA
55 participants
INTERVENTIONAL
2022-01-01
2023-02-01
Brief Summary
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* Measurement of corneal stiffness parameters { Deformation Amlitude (DAR1), Integrated radius, Stress parameter (SP A1), Stress strain index (SSI) and Corvis biomechanical index (CBI) } in keratoconic corneas before and after 3 and 6 months CXL using Corvis ST.
* Measurement of demarcation line depth using anterior segment OCT and correlate between corneal stiffness following CXL and demarcation line depth.
Detailed Description
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Keratoconus is a progressive corneal degeneration resulting from noninflammatory thinning of the corneal stroma. Visual impairment typically commences in adolescence and progresses thereafter. Further increase in myopia, irregular astigmatism, and subepithelial scarring leads to visual impairment. Treatment modalities are based on refractive correction with spectacles or contact lenses to correct astigmatism and restore visual acuity. Such modalities do not stop ectatic progression and further visual deterioration, which ultimately necessitates corneal transplantation in 10% to 20% of patients.
Corneal collagen cross-linking (CXL) has emerged as a promising techniq;ue to slow or halt the progression of keratoconus. CXL leads to an increase in intra and interfibrillar covalent bonds by photosensitized oxidation and causes a biomechanical stabilization of the cornea.
Corneal visualization using dynamic Scheimpflug technology (Corvis ST, Oculus Optikger€ate GmbH) allows in vivo measurement of the corneal biomechanical deformation response to an applied air puff and is useful for evaluating the biomechanical response parameters of the cornea. It captures the dynamic corneal deformation caused by an air puff using an ultrahigh- speed camera that operates at a speed of greater than 4300 frames per second to capture a series of 140 sequential horizontal Scheimpflug images of the temporal-nasal cross section of the cornea. The consistency of the air puff has been shown and the spatial and temporal profiles have been characterized to allow calculation of the load on the cornea within the imaging window.
The Corvis ST enables the measurement of several parameters by analyzing the timing and patterns of deformation at the highest concavity as well as applanation during inward deformation (loading) and outward recovery (unloading). The original parameters have been reported to be influenced most strongly by intraocular pressure (IOP) as well as age and central corneal thickness (CCT). Recently, new corneal biomechanical parameters were introduced, including the Deformation Amplitude ratio at 1.0 mm (DAR1), Deformation Amplitude ratio at 2.0 mm (DAR2), Integrated radius, Stiffness Parameter at first applanation (SP A1), Ambrosio's Relational Thickness (ARTH) , Corbic Biomechanical index (CBI) and biomechanically corrected IOP (bIOP).
Laboratory studies have shown that the effective depth of CXL is confined to the anterior 300 μm of the cornea. Moreover, a stromal demarcation line between treated and untreated stroma was visible biomicroscopically at a depth of approximately 300 μm over the entire cornea after CXL treatment. This demarcation line was also evident on optical coherence tomography (OCT). The depth of this line has been postulated as an indirect measurement of cross-linking effectiveness.
Conditions
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Study Design
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RANDOMIZED
SINGLE_GROUP
* Measurement of demarcation line depth using anterior segment OCT and correlate between corneal stiffness following CXL and demarcation line depth.
DIAGNOSTIC
NONE
Interventions
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Corvis ST (dynamic Scheimpflug technology)
* Measurement of corneal stiffness parameters { Deformation Amlitude (DAR1), Integrated radius, Stress parameter (SP A1), Stress strain index (SSI) and Corvis biomechanical index (CBI) } in keratoconic corneas before and after 3 and 6 months CXL using Corvis ST.
* Measurement of demarcation line depth using anterior segment OCT and correlate between corneal stiffness following CXL and demarcation line depth
Other Intervention Names
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Eligibility Criteria
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Inclusion Criteria
A. ≥ 1.00 diopter increase in maximal keratometry (Kmax). B. ≥ 1.00 diopter increase in the manifest cylinder. C. ≥ 0.75 diopter increase in average of Kmax and Kmin (Kmean). D. ≥ 2% decrease in central thickness. E. ≥ 1.50 diopter increase in the central K power from baseline. F. ≥ 1.0 diopter increase in manifest spherical equivalent change (MRSE).
* All patients have minimal corneal stromal thickness 400 μm before UVA irradiation.
Exclusion Criteria
* Advanced keratoconus with corneal scarring.
* History of herpetic keratitis and severe corneal infection.
* Pregnancy or breastfeeding.
* The use of rigid contact lens¬es for more than 4 weeks before the baseline evaluation.
18 Years
40 Years
ALL
Yes
Sponsors
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Cairo University
OTHER
Responsible Party
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Mohamed Mohamed Samir Elnoamany
Principal Investigator
Principal Investigators
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Mohamed Fakhry, MD
Role: PRINCIPAL_INVESTIGATOR
Cairo University
Central Contacts
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References
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Salouti R, Bagheri M, Shamsi A, Zamani M. Corneal Parameters in Healthy Subjects Assessed by Corvis ST. J Ophthalmic Vis Res. 2020 Feb 2;15(1):24-31. doi: 10.18502/jovr.v15i1.5936. eCollection 2020 Jan-Mar.
Nakao Y, Kiuchi Y, Okumichi H. Evaluation of biomechanically corrected intraocular pressure using Corvis ST and comparison of the Corvis ST, noncontact tonometer, and Goldmann applanation tonometer in patients with glaucoma. PLoS One. 2020 Sep 23;15(9):e0238395. doi: 10.1371/journal.pone.0238395. eCollection 2020.
Herber R, Terai N, Pillunat KR, Raiskup F, Pillunat LE, Sporl E. [Dynamic Scheimpflug Analyzer (Corvis ST) for measurement of corneal biomechanical parameters : A praxis-related overview]. Ophthalmologe. 2018 Aug;115(8):635-643. doi: 10.1007/s00347-018-0716-y. German.
Other Identifiers
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MD-80-2021
Identifier Type: -
Identifier Source: org_study_id