Overview of the Ocular Biomechanical Properties Measured by the Ocular Response Analyzer and the Corvis ST

Purpose. The aim of the study is to investigate the biomechanical properties of the cornea before and after FemtoLASIK in patients with myopia. Material and methods. 24 patients (42 eyes) underwent refractive vision correction using the FemtoLASIK method. The Oculus CORVIS ST ® device (Oculus, Germany) was used to assess the biomechanical properties of the cornea. Results. A statistically significant decrease in the rigidity and strength of the cornea was noted after keratorefractive surgery. Conclusion. Refractive surgery using FemtoLASIK technology leads to a decrease in the rigidity of the cornea, and therefore to a reduction in its framework properties. Key words: refractive surgery, FemtoLASIK, myopia, laser correction, biomechanical properties of the cornea, Oculus CORVIS ST ®.

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Novel Method of Measuring Corneal Viscoelasticity Using the Corvis ST Tonometer

Journal of Clinical Medicine ◽

10.3390/jcm11010261 ◽

2022 ◽

Vol 11 (1) ◽

pp. 261

Author(s):

Agnieszka Boszczyk ◽

Henryk Kasprzak ◽

Joanna Przeździecka-Dołyk

Keyword(s):

Intraocular Pressure ◽

Viscoelastic Properties ◽

High Speed ◽

Central Area ◽

Biomechanical Properties ◽

P Value ◽

Corvis St ◽

Corneal Deformation ◽

The Times ◽

High Repeatability

Background: The process of rapid propagation of the corneal deformation in air puff tonometer depends not only on intraocular pressure, but also on the biomechanical properties of the cornea and anterior eye. One of the biomechanical properties of the cornea is viscoelasticity, which is the most visible in its high-speed deformations. It seems reasonable to link the corneal viscoelasticity parameter to two moments of the highest speed of corneal deformations, when the cornea buckles. The aim of this work is to present a method of determining the time and place of occurrence of corneal buckling, examine spatial and temporal dependencies between two corneal applanations and bucklings in the Corvis ST tonometer, and correlate these dependencies with corneal viscoelastic properties. Methods: Images of the horizontal cross section of the Corvis ST deformed cornea from the air puff tonometer Corvis ST were used. 14 volunteers participated in the study, each of them had one eye measured eight times. Mutual changes in the profile slopes of the deformed corneas were numerically determined. They describe pure corneal deformation, eliminating the influence of rotation, and displacement of the entire eyeball. For each point in the central area of the corneal profile, the maximum velocities of mutual slope changes accompanying the applanations were estimated. The times of their occurrence were adopted as buckling times. Results: The propagation of buckling along the corneal profile is presented, as well as the repeatability and mutual correlations between the buckling parameters and intraocular pressure. Based on the relationship between them, a new parameter describing corneal hysteresis: Corvis Viscoelasticity (CVE) is introduced. It is characterized by high repeatability: ICC = 0.82 (0.69–0.93 CI) and low and insignificant correlation with intraocular pressure: r = 0.25 (p-value = 0.38). Conclusion: The results show for the first time how to measure the corneal buckling and viscoelastic effects with Corvis ST. CVE is a new proposed biomechanical parameter related to the viscoelastic properties of the cornea, which has high repeatability for the examined subject. The distribution of its values is planned to be tested on different groups of patients in order to investigate its clinical applicability.

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Corneal Biomechanical Properties in Varying Severities of Myopia

Frontiers in Bioengineering and Biotechnology ◽

10.3389/fbioe.2020.595330 ◽

2021 ◽

Vol 8 ◽

Author(s):

Mohammad-Reza Sedaghat ◽

Hamed Momeni-Moghaddam ◽

Abbas Azimi ◽

Zohreh Fakhimi ◽

Mohammed Ziaei ◽

...

Keyword(s):

Axial Length ◽

Corneal Thickness ◽

Biomechanical Properties ◽

Cross Sectional Study ◽

Geometrical Parameters ◽

Cross Sectional ◽

Corvis St ◽

Multiple Parameters ◽

Inverse Radius ◽

Biomechanical Parameters

Purpose: To investigate corneal biomechanical response parameters in varying degrees of myopia and their correlation with corneal geometrical parameters and axial length.Methods: In this prospective cross-sectional study, 172 eyes of 172 subjects, the severity degree of myopia was categorized into mild, moderate, severe, and extreme myopia. Cycloplegic refraction, corneal tomography using Pentacam HR, corneal biomechanical assessment using Corvis ST and Ocular Response Analyser (ORA), and ocular biometry using IOLMaster 700 were performed for all subjects. A general linear model was used to compare biomechanical parameters in various degrees of myopia, while central corneal thickness (CCT) and biomechanically corrected intraocular pressure (bIOP) were considered as covariates. Multiple linear regression was used to investigate the relationship between corneal biomechanical parameters with spherical equivalent (SE), axial length (AXL), bIOP, mean keratometry (Mean KR), and CCT.Results: Corneal biomechanical parameters assessed by Corvis ST that showed significant differences among the groups were second applanation length (AL2, p = 0.035), highest concavity radius (HCR, p < 0.001), deformation amplitude (DA, p < 0.001), peak distance (PD, p = 0.022), integrated inverse radius (IR, p < 0.001) and DA ratio (DAR, p = 0.004), while there were no significant differences in the means of pressure-derived parameters of ORA between groups. Multiple regression analysis showed all parameters of Corvis ST have significant relationships with level of myopia (SE, AXL, Mean KR), except AL1 and AL2. Significant biomechanical parameters showed progressive reduction in corneal stiffness with increasing myopia (either with greater negative SE or greater AXL), independent of IOP and CCT. Also, corneal hysteresis (CH) or ability to dissipate energy from the ORA decreased with increasing level of myopia.Conclusions: Dynamic corneal response assessed by Corvis ST shows evidence of biomechanical changes consistent with decreasing stiffness with increasing levels of myopia in multiple parameters. The strongest correlations were with highest concavity parameters where the sclera influence is maximal.

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The changes of corneal biomechanical properties with long-term treatment of prostaglandin analogue measured by Corvis ST

10.21203/rs.3.rs-22280/v3 ◽

2020 ◽

Author(s):

Na Wu ◽

Yuhong Chen ◽

Yaping Yang ◽

Xinghuai Sun

Keyword(s):

Open Angle Glaucoma ◽

Corneal Thickness ◽

Biomechanical Properties ◽

Term Treatment ◽

Prostaglandin Analogue ◽

Corvis St ◽

Long Term Treatment ◽

Corneal Biomechanical Properties

Abstract Background: To investigate the corneal biomechanical changes in primary open angle glaucoma (POAG) patients treated with long-term prostaglandin analogue (PGA). Methods: 111 newly diagnosed POAG patients, including 43 high tension glaucoma (HTG) and 68 normal tension glaucoma (NTG), were measured by Corvis ST to obtain intraocular pressure (IOP), central corneal thickness (CCT) and corneal biomechanical parameters at baseline and at each follow-up visit after initiation of PGA treatment. The follow-up measurements were analyzed by the generalized estimate equation model with an exchangeable correlation structure. Restricted cubic spline was employed to estimate the dose-response relation between follow-up time and corneal biomechanics．Results: The mean follow-up time was 10.3 ± 7.02 months. Deformation amplitude (β=-0.0015, P=0.016), the first applanation velocity (AV1, β=-0.0004, P=0.00058) decreased and the first applanation time (AT1, β=0.0089, P<0.000001) increased statistically significantly with PGA therapy over time after adjusting for age, gender, axial length, corneal curvature, IOP and CCT. In addition, AT1 was lower (7.2950 ± 0.2707 in NTG and 7.5889 ± 0.2873 in HTG, P=0.00011) and AV1 was greater (0.1478 ± 0.0187 in NTG and 0.1314 ± 0.0191 in HTG, P=0.00002) in NTG than in HTG after adjusting for confounding factors.Conclusions: Chronic use of PGA probably influences the corneal biomechanical properties directly, which is to make cornea less deformable. Besides, corneas in NTG tended to be more deformable compared to those in HTG with long-term treatment of PGA.

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Agreement of ocular response analyzer cornea compensated IOP with corvis ST biomechanical IOP following Femtosecond Laser-assisted LASIK

Eye ◽

10.1038/s41433-021-01928-w ◽

2022 ◽

Author(s):

Ramin Salouti ◽

Reza Razeghinejad ◽

Gholamreza Eslami ◽

Mousa Zare ◽

Kia Salouti ◽

...

Keyword(s):

Femtosecond Laser ◽

Ocular Response Analyzer ◽

Corvis St

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Analysis of keratopographic and biomechanical corneal indicators with evaluation of the impact of diagnostic results on myopic refraction patient management tactics

Modern technologies in ophtalmology ◽

10.25276/2312-4911-2021-2-196-199 ◽

2021 ◽

pp. 196-199

Author(s):

D.D. Sibakin ◽

◽

V.A. Breev ◽

E.G. Solodkova ◽

◽

...

Keyword(s):

Patient Management ◽

Screening Program ◽

Clinical Stage ◽

Biomechanical Properties ◽

Corvis St ◽

Stage Of Development ◽

Biomechanical Parameters ◽

The Impact ◽

Biomechanical Measurements ◽

Corneal Biomechanical Properties

Purpose. To analyse keratopographic and biomechanical corneal indicators with the diagnostic results assessment of the influence on the treatment tactics of myopic refraction patient. Materials and methods. Keratotopographic and biomechanical parameters of the cornea in a patient with mild myopia were evaluated. Results. The Belin/Ambrosio (Enchanced Ectasia Display) - BAD keratoconus screening program was used on Pentacam HR, which did not reveal corneal pathology. According to the results of CBI (Corvis biomechanical index) on Corvis ST (OD - 0.61, OS - 0.48), that was indicating poor corneal biomechanical properties and a high risk of keratectasia development. Conclusion. Ophthalmic examination, using The Corvis ST (Oculus, Germany) biomechanical measurements, makes possible to reveal with greater sensitivity subclinical signs of a keratectatic process at the pre-clinical stage of development. Key words: keratotopography, corneal biomechanics, keratoconus.

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Relationship between novel intraocular pressure measurement from Corvis ST and central corneal thickness and corneal hysteresis

British Journal of Ophthalmology ◽

10.1136/bjophthalmol-2019-314370 ◽

2019 ◽

Vol 104 (4) ◽

pp. 563-568 ◽

Cited By ~ 2

Author(s):

Masato Matsuura ◽

Hiroshi Murata ◽

Yuri Fujino ◽

Mieko Yanagisawa ◽

Yoshitaka Nakao ◽

...

Keyword(s):

Intraocular Pressure ◽

Central Corneal Thickness ◽

Linear Regression Analysis ◽

Corneal Thickness ◽

Biomechanical Properties ◽

Applanation Tonometry ◽

Corneal Hysteresis ◽

Corneal Resistance Factor ◽

Corvis St ◽

The Relationship

AimsCorvis ST (CST) yields biomechanical corrected IOP (bIOP) which is purported to be less dependent on biomechanical properties. In our accompanied paper, it was suggested that the repeatability of bIOP is high. The purpose of the current study was to assess the relationship between intraocular pressure (IOP) measured with CST and central corneal thickness (CCT) and corneal hysteresis (CH), in comparison with IOP measured with Goldmann applanation tonometry (GAT) and the ocular response analyzer (ORA).MethodsA total of 141 eyes from 141 subjects (35 healthy eyes and 106 glaucomatous eyes) underwent IOP measurements with GAT, CST and ORA. The relationships between IOP measurements (ORA-IOPg, ORA-IOPcc, CST-bIOP and GAT IOP) and biomechanical properties (CCT, CH and corneal resistance factor (CRF)) were analysed using the linear regression analysis.ResultsIOPg, IOPcc and GAT IOP were significantly associated with CCT (p<0.001), whereas bIOP was not significantly associated with CCT (p=0.19). IOPg, bIOP and GAT IOP were significantly associated with CH (IOPg: p<0.001; bIOP: p<0.001; GAT IOP: p=0.0054), whereas IOPcc was not significantly associated with CH (p=0.18). All of IOP records were associated with CRF (p<0.001).ConclusionThe bIOP measurement from CST is independent from CCT, but dependent on CH and CRF.

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Intraocular pressure measurements in diabetes mellitus

European Journal of Ophthalmology ◽

10.1177/1120672119890517 ◽

2019 ◽

Vol 30 (6) ◽

pp. 1432-1439 ◽

Cited By ~ 1

Author(s):

Lisa Ramm ◽

Robert Herber ◽

Eberhard Spoerl ◽

Lutz E Pillunat ◽

Naim Terai

Keyword(s):

Diabetes Mellitus ◽

Intraocular Pressure ◽

Healthy Subjects ◽

Central Corneal Thickness ◽

Corneal Thickness ◽

Applanation Tonometry ◽

Goldmann Applanation Tonometry ◽

Ocular Response Analyzer ◽

Pressure Measurements ◽

Corvis St

Purpose: To investigate the impact of diabetes mellitus–induced changes on intraocular pressure measurements using Goldmann applanation tonometry, Ocular Response Analyzer, and Corvis ST. Methods: Measurements were done using Goldmann applanation tonometry, Ocular Response Analyzer, and Corvis ST in 69 diabetic patients. Biomechanical-corrected intraocular pressure values by Ocular Response Analyzer (IOPcc) and Corvis ST (bIOP) were used. In addition, biometry and tomography were performed and information on diabetes mellitus specific factors was collected. Results were compared to an age-matched group of 68 healthy subjects. Results: In diabetes mellitus, Goldmann applanation tonometry intraocular pressure (P = 0.193) and central corneal thickness (P = 0.184) were slightly increased. Also, IOPcc (P = 0.075) and bIOP (P = 0.542) showed no significant group difference. In both groups, IOPcc was higher than Goldmann applanation tonometry intraocular pressure (P = 0.002, P < 0.001), while bIOP was nearly equal to Goldmann applanation tonometry intraocular pressure (P = 0.795, P = 0.323). Central corneal thickness showed a tendency to higher values in poorly controlled than in controlled diabetes mellitus (P = 0.059). Goldmann applanation tonometry intraocular pressure correlated to central corneal thickness, while IOPcc and bIOP were independent from central corneal thickness in both groups. All intraocular pressure values showed significant associations to corneal biomechanical parameters. Only in diabetes mellitus, bIOP was correlated to Pachy slope (P = 0.023). Conclusion: In diabetes mellitus, Goldmann applanation tonometry intraocular pressure was slightly, but not significantly, increased, which might be caused by a higher central corneal thickness and changes in corneal biomechanical properties. However, intraocular pressure values measured by Ocular Response Analyzer and Corvis ST were not significantly different between diabetes mellitus patients and healthy subjects. The bIOP showed a higher agreement with Goldmann applanation tonometry than IOPcc and was independent from central corneal thickness.

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