scholarly journals Role of corneal biomechanical properties in predicting of speed of myopic progression in children wearing orthokeratology lenses or single-vision spectacles

2018 ◽  
Vol 3 (1) ◽  
pp. e000204 ◽  
Author(s):  
Kin Wan ◽  
Sin Wan Cheung ◽  
James S Wolffsohn ◽  
Janis B Orr ◽  
Pauline Cho
Keyword(s):  
Axial Length ◽  
Corneal Thickness ◽  
Significant Negative Correlation ◽  
Biomechanical Properties ◽  
Corneal Hysteresis ◽  
Axial Elongation ◽  
Single Vision ◽  
Length Data ◽  
Corneal Biomechanical Properties

ObjectiveTo determine the characteristics of children who were likely to progress rapidly and gain the greatest benefit from orthokeratology (ortho-k) treatment.Methods and analysisThe files of 113 children who participated in two myopia control studies and wore either ortho-k lenses (n=62) or single-vision spectacles (SVS) (n=51) were reviewed. Baseline cycloplegic subjective refraction, central corneal thickness, axial length, keratometry, intraocular pressure, corneal biomechanical properties and 24-month axial length data were retrieved and analysed.ResultsMultivariate analysis showed that there was significant negative correlation between axial elongation and baseline age and corneal hysteresis (p<0.05) in the SVS group. In the ortho-k group, only baseline age was significantly and negatively associated with axial elongation (p<0.01).ConclusionCorneal biomechanical properties and baseline age can predict the rate of axial elongation in myopic children. It may be beneficial for younger myopic children with low corneal hysteresis to commence ortho-k treatment as early as possible.

Influence of corneal biomechanical properties on IOP indices in patients with keratoconus

The Eye ◽  
2019 ◽  
Vol 21 (128) ◽  
pp. 15-19
Author(s):  
Irina Bubnova ◽  
Veronica Averich ◽  
Elena Belousova
Keyword(s):  
Disease Progression ◽  
Corneal Thickness ◽  
Central Zone ◽  
Biomechanical Properties ◽  
Resistance Factor ◽  
Corneal Resistance Factor ◽  
Mean Values ◽  
Coefficient Of Elasticity ◽  
D Values ◽  
Corneal Biomechanical Properties

Purpose: Evaluation of corneal biomechanical prop¬erties and their influence on IOP indices in patients with keratoconus. Material and methods. The study included 194 eyes with keratoconus (113 patients aged from 23 to 36 years old). Corneal refraction in central zone varied from 48.25 to 56.75 D, values of corneal thickness ranged from 279 to 558 μm. Patients were divided into 4 groups according to Amsler classification: I stage – 40 eyes; II stage – 78 eyes; III stage – 54 eyes and IV stage – 22 eyes. Standard ophthal¬mological examination was carried out including pneumo¬tonometry. IOP indices and values of biomechanical prop¬erties were evaluated by dynamic bidirectional pneumatic applanation and pneumatic impression. Results. Study of corneal biomechanical properties in patients with keratoconus showed a decrease of such biomechanical indices as corneal hysteresis (CH) on aver¬age to 8.42±1.12 mm Hg, corneal resistance factor (CRF) – to 7.45±0.96 mm Hg, coefficient of elasticity (CE) – 5.35± 0.87 mm Hg. Values of these indices strongly depended on the stage of keratoconus. In the whole sample, the aver¬age corneal compensated IOP (IOPcc) amounted to 15.08± 2.43 mm Hg, Goldman IOP (IOPg) was 11.61±2.37 mm Hg and pneumatic tonometry IOP (IOPp) was 10.13±2.94 mm Hg. IOPcc indices didn’t have any statistically significant differ¬ence in dependence on the stage of keratoconus (р>0.473), while in process of disease progression IOPg and IOPp indi¬ces showed statistically significant decrease of mean values. Conclusion. Progression of keratoconus led to a de¬crease in corneal biomechanical properties which deter¬mine reduction of such indices as IOPg and IOPp in contrast to IOPcc.

scholarly journals Corneal Biomechanical Properties in Varying Severities of Myopia

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 &lt; 0.001), deformation amplitude (DA, p &lt; 0.001), peak distance (PD, p = 0.022), integrated inverse radius (IR, p &lt; 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.

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

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.

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

2019 ◽  
Vol 104 (4) ◽  
pp. 563-568 ◽  
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.

scholarly journals Corneal Biomechanical Assessment Using Corneal Visualization Scheimpflug Technology in Keratoconic and Normal Eyes

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Lei Tian ◽  
Yi-Fei Huang ◽  
Li-Qiang Wang ◽  
Hua Bai ◽  
Qun Wang ◽  
...  
Keyword(s):  
Intraocular Pressure ◽  
Corneal Thickness ◽  
Area Under The Curve ◽  
Biomechanical Properties ◽  
Corvis St ◽  
Biomechanical Assessment ◽  
Deformation Amplitude ◽  
Biomechanical Parameters ◽  
And Control ◽  
Corneal Biomechanical Properties

Purpose. To compare the corneal biomechanical properties of keratoconic patients and age-matched controls using corneal visualization Scheimpflug technology (Corvis ST).Methods. Sixty keratoconic eyes from 47 keratoconus patients and 60 normal eyes from 60 controls were enrolled in this prospective study. Tomography and biomechanical parameters of all eyes were obtained with the Pentacam and Corvis ST, respectively. Intraocular pressure was measured using a Goldmann applanation tonometer.Results.The tomography and biomechanical parameters of the keratoconic corneas were significantly different from those of the normal corneas except for the anterior chamber angle, first applanation length, the highest concavity time, and peak distance. The deformation amplitude was the best predictive parameter (area under the curve: 0.882), with a sensitivity of 81.7%, although there was a significant overlap between keratoconic and normal corneas that ranged from 1.0 to 1.4 mm. In both the keratoconus and control groups, the deformation amplitude was negatively correlated with intraocular pressure, central corneal thickness, and corneal volume at 3 and 5 mm.Conclusions. Corvis ST offers an alternative method for measuring corneal biomechanical properties. The possibility of classifying keratoconus based on deformation amplitude deserves clinical attention.

Relationship between Corneal Biomechanical Properties and Optic Nerve Head Changes after Deep Sclerectomy

2017 ◽  
Vol 27 (5) ◽  
pp. 535-541 ◽  
Author(s):  
Laura Díez-Álvarez ◽  
Francisco J. Muñoz-Negrete ◽  
Pilar Casas-Llera ◽  
Noelia Oblanca ◽  
Victoria de Juan ◽  
...  
Keyword(s):  
Optic Nerve ◽  
Optic Nerve Head ◽  
Open Angle Glaucoma ◽  
Biomechanical Properties ◽  
Resistance Factor ◽  
Corneal Hysteresis ◽  
Enhanced Depth Imaging ◽  
Deep Sclerectomy ◽  
Corneal Resistance Factor ◽  
Corneal Biomechanical Properties

Purpose To evaluate corneal biomechanical properties and optic nerve head (ONH) changes following deep sclerectomy (DS) and the relation to each other. Methods Forty-nine eyes with primary open-angle glaucoma that underwent DS were studied. Corneal biomechanical properties were assessed using the Ocular Response Analyzer and the ONH was evaluated by Spectralis optical coherence tomography with enhanced depth imaging technology before surgery and 3 months postoperatively. Changes in corneal hysteresis (CH), corneal resistance factor (CRF), optic nerve cupping, prelaminar tissue thickness, and lamina cribrosa depth and thickness were registered. A correlation matrix and multiple linear regression models were used to determine predictors of ONH changes. Results At 3 months after surgery, mean corneal compensated intraocular pressure (IOPcc) significantly decreased by 27.9% (p<00.001) and mean Goldmann-correlated IOP (IOPg) decreased by 30.52% (p<00.001). Mean CH increased and CRF decreased by 18.4% and 10.1%, respectively (p<00.001). There was a significant reversal of ONH cupping mainly due to a prelaminar tissue thickening (p<00.001). Significant associations were found between ONH cupping reversal and prelaminar tissue thickening with preoperative IOPcc (p = 0.046), IOPg (p = 0.02), and CRF (p = 0.002) and with changes in IOP, CH, and CRF (p<00.001, p = 0.004, p = 0.018, respectively) after surgery. Conclusions Corneal hysteresis increased and CRF decreased significantly 3 months after DS. Corneal resistance factor was the single largest preoperative factor influencing cupping reversal changes. Despite the influence of preoperative variables, postoperative IOP reduction was the only independent factor influencing changes observed in the ONH after surgery.

Ocular Response Analyser — a New Diagnostic Tool to Measure Corneal Biomechanical Properties and Intraocular Pressure

1970 ◽  
Vol 12 (3) ◽  
pp. 159-168
Author(s):  
Arulmozhi Varman ◽  
Muthuraman Chockalingam
Keyword(s):  
Intraocular Pressure ◽  
Diagnostic Tool ◽  
Pressure Measurement ◽  
Corneal Thickness ◽  
Biomechanical Properties ◽  
Ocular Diseases ◽  
Wide Range ◽  
Corneal Biomechanical Properties ◽  
Ocular Response Analyser

Corneal biomechanical properties have been known to influence the outcome of ocular measurements and procedures for a wide range of ocular diseases. The assessment of corneal biomechanical properties has been a challenge and, for this reason, measurement of the geographical parameters of the cornea, namely corneal thickness and topography, has formed the mainstay of understanding the basis of various ocular pathologies. A newly marketed instrument, the Reichert ocular response analyser has been developed to improve the accuracy of intraocular pressure measurement by uniquely measuring and integrating corneal biomechanical data into its intraocular pressure estimates.

scholarly journals Corneal Biomechanical Properties after FS-LASIK with Residual Bed Thickness Less Than 50% of the Original Corneal Thickness

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Haixia Zhang ◽  
Muhammad Ahmad Khan ◽  
Di Zhang ◽  
Xiao Qin ◽  
Ding Lin ◽  
...  
Keyword(s):  
Elastic Moduli ◽  
Corneal Thickness ◽  
Tensile Tests ◽  
Biomechanical Properties ◽  
Uniaxial Tensile ◽  
Stress Region ◽  
Bed Thickness ◽  
Limit Stress ◽  
The Right ◽  
Corneal Biomechanical Properties

Background. The changes in corneal biomechanical properties after LASIK remain an unknown but important topic for surgical design and prognostic evaluation. This study aims to observe the postoperative corneal biomechanical properties one month after LASIK with amount of corneal cutting (ACC) greater than 50% of the central corneal thickness (CCT). Methods. FS-LASIK was performed in 10 left rabbit eyes with ACC being 60% (L60) and 65% (L65) of the CCT, while the right eyes (R) were the control. After 4 weeks, rabbits were executed and corneal strip samples were prepared for uniaxial tensile tests. Results. At the same strain, the stresses of L65 and L60 were larger than those of R. The elastic moduli of L60 and L65 were larger than those of R when the stress was 0.02 MPa, while they began to be less than those of R when stress exceeds the low-stress region. After 10 s relaxation, the stress of specimens L65, L60, and R increased in turn. Conclusion. The elastic moduli of the cornea after FS-LASIK with ACC greater than 50% of the CCT do not become less under normal rabbit IOP. The limit stress grows with the rise of ACC when relaxation becomes stable.

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