scholarly journals Relationship among Corneal Biomechanics, Anterior Segment Parameters, and Geometric Corneal Parameters

2016 ◽  
Vol 2016 ◽  
pp. 1-7 ◽  
Author(s):  
Sadık Görkem Çevik ◽  
Sertaç Argun Kıvanç ◽  
Berna Akova-Budak ◽  
Mediha Tok-Çevik
Keyword(s):  
Corneal Thickness ◽  
Anterior Segment ◽  
Biomechanical Properties ◽  
Negative Association ◽  
Corneal Resistance Factor ◽  
Multivariate Models ◽  
Corrected Visual Acuity ◽  
Biomechanical Parameters ◽  
Anterior Segment Parameters ◽  
The Relationship

Purpose. To investigate the relationship between corneal biomechanical parameters, anterior segment parameters, and geometric corneal parameters in a healthy Caucasian group. Methods. This retrospective study included the healthy eyes with best corrected visual acuity of at least 20/40 of 122 Caucasian subjects. The anterior segment parameters and geometric corneal parameters such as corneal volume, central corneal thickness, horizontal and vertical corneal radii, anterior and posterior steep, and flat keratometric values were measured with a Scheimpflug camera. The biomechanical properties were measured with Ocular Response Analyzer. Results. One hundred and twenty-two healthy Caucasian subjects (67 males, 55 females) with a mean age of 45.32±20.23 were enrolled. Both corneal hysteresis and corneal resistance factor were positively correlated with CCT (r=0.529, p<0.001; r=0.638, p<0.001) and CV (r=0.635, p<0.001; r=0.579, p<0.001) and negatively correlated with age (r=-0.373, p<0.001; r=-0.249, p<0.001). Both in age-gender and multivariate models, CH and CRF had statistically significant negative association with the posterior steep K value. Conclusions. CH and CRF are negatively correlated with posterior steep and average posterior K values.

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 Relationship between Corneal Morphogeometrical Properties and Biomechanical Parameters Derived from Dynamic Bidirectional Air Applanation Measurement Procedure in Keratoconus

Diagnostics ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 640
Author(s):  
Francisco Cavas ◽  
David Piñero ◽  
José S. Velázquez ◽  
Jorge Mira ◽  
Jorge L. Alió
Keyword(s):  
Corneal Thickness ◽  
Biomechanical Properties ◽  
Measurement Procedure ◽  
Volumetric Analysis ◽  
Diagnostic Tools ◽  
In Vivo Evaluation ◽  
Topographic Analysis ◽  
Biomechanical Parameters ◽  
The Relationship

The morphogeometric analysis of the corneal structure has become a clinically relevant diagnostic procedure in keratoconus (KC) as well as the in vivo evaluation of the corneal biomechanical properties. However, the relationship between these two types of metrics is still not well understood. The current study investigated the relationship of corneal morphogeometry and volume with two biomechanical parameters: corneal hysteresis (CH) and corneal resistance factor (CRF), both provided by an Ocular Response Analyzer (Reichert). It included 109 eyes from 109 patients (aged between 18 and 69 years) with a diagnosis of keratoconus (KC) who underwent a complete eye examination including a comprehensive corneal topographic analysis with the Sirius system (CSO). With the topographic information obtained, a morphogeometric and volumetric analysis was performed, defining different variables of clinical use. CH and CRF were found to be correlated with these variables, but this correlation was highly influenced by corneal thickness. This suggests that the mechanical properties of KC cornea contribute only in a partial and limited manner to these biomechanical parameters, being mostly influenced by morphogeometry under normal intraocular pressure levels. This would explain the limitation of CH and CRF as diagnostic tools for the detection of incipient cases of KC.

scholarly journals Correlation Between Corneal Biomechanics and Anterior Segment Parameters in Healthy Saudi Females

2020 ◽  
Author(s):  
Amira Elagamy ◽  
Rawan Al-Amri ◽  
Mohamed Berika
Keyword(s):  
Saudi Arabia ◽  
Anterior Chamber ◽  
Corneal Thickness ◽  
Anterior Segment ◽  
Corneal Biomechanics ◽  
Positive Correlation ◽  
Pearson's Correlation ◽  
Biomechanical Parameters ◽  
Anterior Segment Parameters ◽  
Healthy Eyes

Abstract Background: The ocular response analyzer (ORA) can measure corneal hysteresis (CH), corneal resistance factor (CRF), Goldmann correlated IOP (IOPg) and corneal compensated intraocular pressure (IOPcc).1 Anterior segment parameters such as central corneal thickness (CCT), thinnest corneal thickness (TCT), apex corneal thickness (Apex CT), corneal volume (CV), anterior chamber depth (ACD), anterior chamber volume (ACV) and corneal astigmatism (CA) can be measured by Pentacam which is a Scheimpflug imaging device.2 Many studies 3-10 investigated the correlation between corneal biomechanics and anterior segment parameters in healthy eyes and demonstrated a strong correlation between CH, CRF with CCT. Hwang et al 2013 7 found that CV was positively correlated with CH, but not CRF. However, Çevik et al 2016 10 reported positive correlations between CH, CRF, and CV and negative correlations between CH, CRF and both of posterior steep and average posterior 𝐾 values. Hwang et al 2 did not show a significant association between CA and all the biomechanical properties. Conversely, Montard et al 4 reported a negative association between CA with CH and CRF. Therefore, there is still debate regarding evaluation of this relation. Up to our knowledge, the correlation between corneal biomechanics and anterior segment parameters in healthy eyes is never investigated in Saudi Arabia.The purpose of this study was conducted to evaluate the correlation between corneal biomechanics measured with ORA and anterior segment parameters assessed with Oculus Pentacam HR in healthy Saudi females.Methods: This study was a prospective, non-randomized, cross-sectional, observational and quantitative study. The study included 129 eyes of 129 healthy Saudi females from King Saud University, Riyadh, Saudi Arabia. The mean age was 19.87 ± 1.328 (18 – 29 years). All subjects underwent a comprehensive ophthalmologic examination including refraction, visual acuity measurement, slit-lamp biomicroscopic examination, IOP measurement with an air puffer tonometer, and funduscopy. In addition, anterior segment parameters were measured with Oculus Pentacam HR. Additionally, corneal biomechanical parameters were measured with ORA (Reichert Ophthalmic Instruments). All data was analyzed using a Statistical Package for the Social Sciences (SPSS) version 22.0 software (SPSS Inc., Chicago, II, USA). Associations between corneal biomechanical parameters and anterior segment parameters were analyzed by Pearson’s Correlation coefficients. P < 0.05 was considered a statistically significant.Results: In this study, mean (±SD) spherical equivalent (SE) was -1.62 ± 2.15 diopters and mean (±SD) CCT was 552.41 ± 58.90 μm. Mean (±SD) CH and CRF were 11.61 ± 1.80 and 11.26 ± 1.99 mm Hg, respectively. Correlation between ORA parameters and the anterior segment parameters using Pearson’s Correlation Coefficient for all eyes in this study showed only highly significant positive correlation between CCT and each of CH, CRF, IOP g (r = 0.381, P < 0.0001) (r = 0.395, P < 0.0001) (r = 0.304, P < 0.0001) respectively. On the other hand, no significant association was detected between IOP cc and anterior segment parameters in this study Conclusion: This work is the first one in Saudi Arabia to evaluate the correlation between corneal biomechanics and anterior segment parameters in healthy Saudi females. This study reported a positive correlation between CCT and each of CH, CRF, IOPg. Mild myopic eyes in this study showed a positive association between ASKV and each of CH and CRF. In addition, the mild myopic eyes demonstrated a positive relation between IOP g and ACV. Future prospective studies including males, different ethnic populations, different age groups with large sample sizes, using different imaging techniques, are recommended.

scholarly journals Corneal biomechanical properties in myopic eyes evaluated via Scheimpflug imaging

2020 ◽  
Author(s):  
A-Yong Yu ◽  
Hui Shao ◽  
Anpeng Pan ◽  
Qinmei Wang ◽  
Zixu Huang ◽  
...  
Keyword(s):  
Anterior Segment ◽  
Biomechanical Properties ◽  
Control Group ◽  
Spherical Equivalent ◽  
Corvis St ◽  
Scheimpflug Imaging ◽  
Biomechanical Parameters ◽  
Anterior Segment Parameters ◽  
Corneal Biomechanical Properties ◽  
Myopia Control

Abstract Background To investigate the biomechanical properties of the cornea in myopic eyes using corneal visualization scheimpflug technology (Corvis ST). The relationships between the biomechanical properties of the cornea and the degree of myopia were also investigated.Methods 265 eyes of 265 subjects were included. According to spherical equivalent (SE) in diopters (D), participants were divided into four groups: low myopia/control group (SE: -0.50 to -3.00D), moderate myopia group (SE: -3.00 to -6.00D), high myopia group (SE: -6.00 to -10.00D) and severe myopia group (SE greater than -10.00D). Axial length (AL), anterior segment parameters, and corneal biomechanical properties were obtained with the Lenstar LS900, Pentacam HR and Corvis ST, respectively. Results Mean (±SD) SE was -7.29±4.31D (range: -0.63 to -25.75D). Mean AL was 26.31±1.82mm (range: 21.87 to 31.94mm). Significant differences were detected within the four groups in terms of six corneal biomechanical parameters: deformation amplitude (DA), time from start until second applanation (A2-time), length of flattened cornea at the second applanation (A2-length), corneal velocity during the first and second applanation (A2-velocity), time from start to highest concavity (HC-time), and central curvature at highest concavity (HC radius). DA was positively correlated with AL ( r =0.16, P =0.009) and negatively correlated with SE ( r =-0.20, P =0.001). A2-time, A2-velocity, A2-length and HC-time were positively correlated with SE and negatively correlated with AL.Conclusions The alterations in corneal biomechanics may be associated with the degree of myopia. DA and A2-velocity may be useful corneal biomechanical indicators in patients with myopia.

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 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.

Evaluation and grading of Kayser–Fleischer ring in Wilson disease by Scheimpflug camera

2020 ◽  
pp. 112067212093102
Author(s):  
Cumali Degirmenci ◽  
Melis Palamar
Keyword(s):  
Wilson Disease ◽  
Corneal Thickness ◽  
Anterior Segment ◽  
Serum Ceruloplasmin ◽  
Endothelial Surface ◽  
Ceruloplasmin Level ◽  
Urinary Copper ◽  
Scheimpflug Imaging ◽  
Anterior Segment Parameters ◽  
Grade 3

Purpose: Evaluation the anterior segment parameters of Wilson disease patients with Kayser–Fleischer ring, the diagnostic power of Scheimpflug imaging for Kayser–Fleischer ring and suggest a scoring system. Materials and Methods: A total of 44 eyes of 22 Wilson disease patients with Kayser–Fleischer ring and 40 right eyes of 40 healthy age matched subjects were enrolled to the study. Serum ceruloplasmin and urine copper/24 hours levels were recorded. Anterior segment parameters including steep and flat keratometry, corneal thickness at central, 2, 4, 6, 8 and 10 mm, anterior chamber angle width, volume and depth, corneal volume, pupillary diameter were evaluated by Scheimpflug imaging. Images of cornea were scored according to Kayser–Fleischer ring size. Results: Serum ceruloplasmin level was below 10 mg/dL in 17 patients and was 12, 18.5, 20, 22, 37 mg/dl in the remaining five patients. Urinary copper/24 hours was 249.55 ± 304.14 (23–1050) µg/day. Central corneal thickness and corneal thickness at 2 mm were statistically different ( p values 0.02, 0.04, respectively). Scheimpflug images apparently showed Kayser–Fleischer ring as a hyper-reflective band at the corneal endothelial surface. Kayser–Fleischer ring in 24 eyes was grade 1, 16 eyes were grade 2 and 4 eyes were grade 3. Conclusion: Scheimpflug imaging seems to be a helpful diagnostic tool for detecting and grading the Kayser–Fleischer ring. Corneal thickness in Wilson disease patients with Kayser–Fleischer ring tends to be higher, so that the possible affection in corneal thickness should be kept in mind for clinical evaluation of these patients.

scholarly journals In VivoCorneal Biomechanical Properties with Corneal Visualization Scheimpflug Technology in Chinese Population

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Ying Wu ◽  
Lei Tian ◽  
Yi-fei Huang
Keyword(s):  
Linear Regression ◽  
Healthy Subjects ◽  
Chinese Population ◽  
Regression Models ◽  
Corneal Thickness ◽  
Intraclass Correlation ◽  
Biomechanical Properties ◽  
Linear Regression Models ◽  
Corneal Volume ◽  
Biomechanical Parameters

Purpose. To determine the repeatability of recalculated corneal visualization Scheimpflug technology (CorVis ST) parameters and to study the variation of biomechanical properties and their association with demographic and ocular characteristics.Methods. A total of 783 healthy subjects were included in this study. Comprehensive ophthalmological examinations were conducted. The repeatability of the recalculated biomechanical parameters with 90 subjects was assessed by the coefficient of variation (CV) and intraclass correlation coefficient (ICC). Univariate and multivariate linear regression models were used to identify demographic and ocular factors.Results. The repeatability of the central corneal thickness (CCT), deformation amplitude (DA), and first/second applanation time (A1/A2-time) exhibited excellent repeatability (CV%≤3.312% and ICC≥0.929 for all measurements). The velocity in/out(Vin/out), highest concavity- (HC-) radius, peak distance (PD), and DA showed a normal distribution. Univariate linear regression showed a statistically significant correlation betweenVin,Vout, DA, PD, and HC-radius and IOP, CCT, and corneal volume, respectively. Multivariate analysis showed that IOP and CCT were negatively correlated withVin, DA, and PD, while there was a positive correlation betweenVoutand HC-radius.Conclusion. The ICCs of the recalculated parameters, CCT, DA, A1-time, and A2-time, exhibited excellent repeatability. IOP, CCT, and corneal volume significantly influenced the biomechanical properties of the eye.

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