Corneal biomechanics study (1): Central corneal thickness versus corneal resistance factor

2009 ◽  
Vol 87 ◽  
pp. 0-0
Author(s):  
Z VALYI ◽  
J IBANEZ ◽  
D PEREZ GARCíA ◽  
B JIMENEZ DEL RIO ◽  
JA CRISTOBAL
Keyword(s):  
Central Corneal Thickness ◽  
Corneal Thickness ◽  
Resistance Factor ◽  
Corneal Biomechanics ◽  
Corneal Resistance Factor

scholarly journals Biomechanical Properties in Different Types of Thin Corneas in Menoufia Population

2020 ◽  
Author(s):  
Adel Galal Zaky ◽  
Amin Faisal Ellakwa ◽  
Ahmed Ibrahim Basiony
Keyword(s):  
Central Corneal Thickness ◽  
Corneal Thickness ◽  
Study Groups ◽  
Biomechanical Properties ◽  
Resistance Factor ◽  
Corneal Hysteresis ◽  
Corneal Resistance Factor ◽  
Significant Difference ◽  
Different Types ◽  
The Mean

Abstract Background:To evaluate and compare corneal hysteresis (CH) and corneal resistance factor (CRF) in normal thin (NT) healthy corneas with central corneal thickness (CCT) 470-500 µm with matched thickness in keratoconus suspect (KCS) and keratoconus (KC) and eyes.Methods: A total of 103 eyes in three groups were included prospectively: NT, KCS and KC groups based on clinical examination and pentacam findings. Corneal hysteresis (CH) and corneal resistance factor (CRF) were measured by the ocular response analyzer (ORA). CCT ,CH and CRF were compared between the three groups and statistically analyzed by variance tests.Results:The three groups consisted of 44 NT, 26 KCS, and 33 KC. The mean CH measured was 8.689 ± 1.775, 9.051 ± 1.1190 and 8.129 ± 0.8539 mmHg in NT, KCS and KC eyes, respectively. The mean CRF was 8.441 ± 1.663, 8.337 ± 1.114 and 7.2422 ± 1.3110 mmHg in NT, KCS and KC eyes, respectively. Within range of central corneal thickness (470 – 500 µm), only mean CRF was statistically significantly different between the NT and KC (P < 0.05); there was no statistically significant difference between NT and KCS, nor the mean CH between each group (P > 0.05).Conclusions: CRF only can be helpful in differentiating KC from NT eyes; KCS could not be predicted with either corneal biomechanical metrics. No benefit from CH in differentiating between the three study groups.

scholarly journals Corneal biomechanical metrics in thin cornea of normal, keratoconus suspect and keratoconus in Egyptian population

2019 ◽  
Author(s):  
Adel Galal Zaky ◽  
Mohamed Samy Abd Elaziz ◽  
Hatem Mohamed Marey ◽  
Moatz Faiz Elsawy ◽  
Nermeen Mahmoud Badawi ◽  
...  
Keyword(s):  
Central Corneal Thickness ◽  
Corneal Thickness ◽  
Study Groups ◽  
Resistance Factor ◽  
Corneal Hysteresis ◽  
Main Concern ◽  
Test Results ◽  
Corneal Resistance Factor ◽  
Significant Difference ◽  
The Mean

Abstract Background To assess and compare corneal hysteresis (CH) and corneal resistance factor (CRF) in normal thin (NT) healthy corneas with central corneal thickness (CCT) 470-500 µm with matched thickness in keratoconus (KC) and keratoconus suspect (KCS) eyes. Methods A total of 66 eyes in three groups were included prospectively: NT, KCS and KC groups based on clinical examination and topography. Corneal hysteresis (CH) and corneal resistance factor (CRF) were measured by the ocular response analyzer. CH and CRF were compared between the three groups and statistically analyzed by variances test. Results The three groups consisted of 32 NT, 19 KCS, and 15 KC. The mean CH measured was 8.55± 1.77, 9.03± 1.119 and 8.06 ± 0.85 mm Hg in NT, KCS and KC eyes, respectively. The mean CRF was 8.39 ± 1.47, 8.27 ± 1.09 and 7.24 ± 1.27 mm Hg in NT, KCS and KC eyes, respectively. Within range of central corneal thickness (470 – 500 µm), only mean CRF was statistically significantly different between the NT and KC (P < 0.05); there was no statistically significant difference between NT and KCS, nor the mean CH between each groups (P > 0.05). Conclusions CRF only can be helpful in differentiating KC from NT eyes; however, it’s not valuable for detecting KCS which is the main concern for refractive surgery. No benefit from CH in differentiating between the study groups. Further investigations & work focusing on more accurate tests for identifying KCS are still needed.

Changes in corneal biomechanics during pregnancy in Chinese healthy female

2020 ◽  
pp. 112067212090203
Author(s):  
Yaping Yang ◽  
Jun Ye ◽  
Tsz Kin Ng ◽  
Na Wu ◽  
Xinghuai Sun ◽  
...  
Keyword(s):  
Intraocular Pressure ◽  
Pregnant Women ◽  
Central Corneal Thickness ◽  
Corneal Thickness ◽  
Resistance Factor ◽  
Corneal Hysteresis ◽  
Corneal Resistance Factor ◽  
Third Trimester ◽  
The Third ◽  
Healthy Female

Purpose: To evaluate the changes of corneal biomechanics and the intraocular pressure during pregnancy in a Chinese healthy female population. Methods: A total of 222 unrelated Chinese females were recruited: 52 non-pregnant, 15 pregnant in the first trimester, 68 pregnant in the second trimester, and 87 pregnant in the third trimester. The intraocular pressure and corneal biomechanical parameters, including corneal-compensated intraocular pressure, Goldmann-correlated intraocular pressure, corneal hysteresis, and corneal resistance factor, were measured by an Ocular Response Analyzer G3. Central corneal thickness was measured by Lenstar (LS900). Results: Corneal hysteresis and corneal resistance factor were significantly higher in pregnant women at the second and third trimesters. Corneal-compensated intraocular pressure was lower in women at the third trimester of pregnancy ( p = 0.023), but the difference became insignificant after adjustment for corneal hysteresis. Central corneal thickness was marginally higher in pregnant women than non-pregnant women ( p = 0.032). There was a negative correlation between corneal-compensated intraocular pressure and corneal hysteresis ( r = −0.337, p < 0.001) and a positive correlation between central corneal thickness and corneal hysteresis ( r = 0.711, p < 0.0001). After adjustment for corneal-compensated intraocular pressure, corneal hysteresis remained significantly higher in the second and third trimesters of pregnant women than non-pregnant women ( p = 0.031, p = 0.005). Conclusion: This study revealed a significant increase in corneal hysteresis and corneal resistance factor in the second and third trimesters. The increase of corneal hysteresis was independent of corneal-compensated intraocular pressure, indicating pregnant females have unique characteristics in corneal-compensated intraocular pressure and corneal biomechanical properties that may be related to glaucoma and corneal ectatic diseases in pregnancy.

scholarly journals Biomechanical Properties in Different Types of Thin Corneas in Menoufia Population

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Adel Galal Zaky ◽  
Amin Faisal Ellakwa ◽  
Ahmed Ibrahim Basiony
Keyword(s):  
Central Corneal Thickness ◽  
Corneal Thickness ◽  
Study Groups ◽  
Biomechanical Properties ◽  
Resistance Factor ◽  
Corneal Hysteresis ◽  
Corneal Resistance Factor ◽  
Significant Difference ◽  
Different Types ◽  
The Mean

Background. To evaluate and compare corneal hysteresis (CH) and corneal resistance factor (CRF) in normal thin (NT) healthy corneas with central corneal thickness (CCT) of 470–500 μm with matched thickness in keratoconus suspect (KCS) and keratoconus (KC) eyes. Methods. A total of 103 eyes in three groups were included prospectively: NT, KCS, and KC groups based on clinical examination and Pentacam findings. Corneal hysteresis (CH) and corneal resistance factor (CRF) were measured using the ocular response analyzer (ORA). CCT, CH, and CRF were compared between the three groups and statistically analyzed by variance tests. Results. The three groups consisted of 44 NT, 26 KCS, and 33 KC. The mean CH measured was 8.689 ± 1.775, 9.051 ± 1.1190, and 8.129 ± 0.8539 mmHg in NT, KCS, and KC eyes, respectively. The mean CRF was 8.441 ± 1.663, 8.337 ± 1.114, and 7.2422 ± 1.3110 mmHg in NT, KCS, and KC eyes, respectively. Within the range of central corneal thickness (470–500 μm), only mean CRF was statistically significantly different between the NT and KC ( P < 0.05 ); there was no statistically significant difference between NT and KCS, nor was the mean CH between each group ( P > 0.05 ). Conclusions. CRF only can be helpful in differentiating KC from NT eyes; KCS could not be predicted with either corneal biomechanical metrics. There was no benefit from CH in differentiating between the three study groups.

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.

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 Fine-mapping and cell-specific enrichment at corneal resistance factor loci prioritize candidate causal regulatory variants

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Xinyi Jiang ◽  
Nefeli Dellepiane ◽  
Erola Pairo-Castineira ◽  
Thibaud Boutin ◽  
Yatendra Kumar ◽  
...  
Keyword(s):  
Fine Mapping ◽  
Association Studies ◽  
Corneal Thickness ◽  
Corneal Stroma ◽  
Resistance Factor ◽  
Open Chromatin ◽  
Human Cornea ◽  
Genome Wide Association Studies ◽  
Corneal Resistance Factor ◽  
Matrix Gene

AbstractCorneal resistance factor (CRF) is altered during corneal diseases progression. Genome-wide-association studies (GWAS) indicated potential CRF and disease genetics overlap. Here, we characterise 135 CRF loci following GWAS in 76029 UK Biobank participants. Enrichment of extra-cellular matrix gene-sets, genetic correlation with corneal thickness (70% (SE = 5%)), reported keratoconus risk variants at 13 loci, all support relevance to corneal stroma biology. Fine-mapping identifies a subset of 55 highly likely causal variants, 91% of which are non-coding. Genomic features enrichments, using all associated variants, also indicate prominent regulatory causal role. We newly established open chromatin landscapes in two widely-used human cornea immortalised cell lines using ATAC-seq. Variants associated with CRF were significantly enriched in regulatory regions from the corneal stroma-derived cell line and enrichment increases to over 5 fold for variants prioritised by fine-mapping-including at GAS7, SMAD3 and COL6A1 loci. Our analysis generates many hypotheses for future functional validation of aetiological mechanisms.

Are There Any Changes in Corneal Biomechanics and Central Corneal Thickness in Fuchs’ Uveitis?

2015 ◽  
Vol 24 (5) ◽  
pp. 561-567 ◽  
Author(s):  
Emine Sen ◽  
Pinar Ozdal ◽  
Melike Balikoglu-Yilmaz ◽  
Pinar Nalcacioglu Yuksekkaya ◽  
Ufuk Elgin ◽  
...  
Keyword(s):  
Central Corneal Thickness ◽  
Corneal Thickness ◽  
Corneal Biomechanics

scholarly journals Multivariate Analysis of the Ocular Response Analyzer’s Corneal Deformation Response Curve for Early Keratoconus Detection

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Jonatán D. Galletti ◽  
Pablo R. Ruiseñor Vázquez ◽  
Fernando Fuentes Bonthoux ◽  
Tomás Pförtner ◽  
Jeremías G. Galletti
Keyword(s):  
Factor Analysis ◽  
Multivariate Analysis ◽  
Diagnostic Performance ◽  
Corneal Thickness ◽  
Biomechanical Testing ◽  
Case Series ◽  
Resistance Factor ◽  
Analysis Model ◽  
Corneal Resistance Factor ◽  
Corneal Deformation

Purpose. To thoroughly analyze corneal deformation responses curves obtained by Ocular Response Analyzer (ORA) testing in order to improve subclinical keratoconus detection.Methods. Observational case series of 87 control and 73 subclinical keratoconus eyes. Examination included corneal topography, tomography, and biomechanical testing with ORA. Factor analysis, logistic regression, and receiver operating characteristic curves were used to extract combinations of 45 corneal waveform descriptors. Main outcome measures were corneal-thickness-corrected corneal resistance factor (ccCRF), combinations of corneal descriptors, and their diagnostic performance.Results. Thirty-seven descriptors differed significantly in means between groups, and among them ccCRF afforded the highest individual diagnostic performance. Factor analysis identified first- and second-peak related descriptors as the most variable one. However, conventional biomechanical descriptors corneal resistance factor and hysteresis differed the most between control and keratoconic eyes. A combination of three factors including several corneal descriptors did not show better diagnostic performance than a combination of conventional indices.Conclusion. Multivariate analysis of ORA signals did not surpass simpler models in subclinical keratoconus detection, and there is considerable overlap between normal and ectatic eyes irrespective of the analysis model. Conventional biomechanical indices seem to already provide the best performance when appropriately considered.

Sign in / Sign up

Export Citation Format

Share Document