scholarly journals Fibril density reduction in keratoconic corneas

2021 ◽  
Vol 18 (175) ◽  
Author(s):  
Dong Zhou ◽  
Ahmed Abass ◽  
Bernardo Lopes ◽  
Ashkan Eliasy ◽  
Sally Hayes ◽  
...  
Keyword(s):  
Collagen Fibril ◽  
Corneal Thickness ◽  
Minimum Thickness ◽  
Distribution Maps ◽  
Topographic Features ◽  
Refractive Power ◽  
Density Reduction ◽  
Significant Difference ◽  
The Mean ◽  
Stiffness Distribution

This study aims to estimate the reduction in collagen fibril density within the central 6 mm radius of keratoconic corneas through the processing of microstructure and videokeratography data. Collagen fibril distribution maps and topography maps were obtained for seven keratoconic and six healthy corneas, and topographic features were assessed to detect and calculate the area of the cone in each keratoconic eye. The reduction in collagen fibril density within the cone area was estimated with reference to the same region in the characteristic collagen fibril maps of healthy corneas. Together with minimum thickness and mean central corneal refractive power, the cone area was correlated with the reduction in the cone collagen fibrils. For the corneas considered, the mean area of keratoconic cones was 3.30 ± 1.90 mm 2 . Compared with healthy corneas, fibril density in the cones of keratoconic corneas was lower by as much as 35%, and the mean reduction was 17 ± 10%. A linear approximation was developed to relate the magnitude of reduction to the refractive power, minimum corneal thickness and cone area ( R 2 = 0.95, p < 0.001). Outside the cone area, there was no significant difference between fibril arrangement in healthy and keratoconic corneas. The presented method can predict the mean fibril density in the keratoconic eye's cone area. The technique can be applied in microstructure-based finite-element models of the eye to regulate its stiffness level and the stiffness distribution within the areas affected by keratoconus.

scholarly journals Corneal Biomechanical Parameters and Central Corneal Thickness in Glaucoma Patients, Glaucoma Suspects, and a Healthy Population

2021 ◽  
Vol 10 (12) ◽  
pp. 2637
Author(s):  
Mª. Ángeles del Buey-Sayas ◽  
Elena Lanchares-Sancho ◽  
Pilar Campins-Falcó ◽  
María Dolores Pinazo-Durán ◽  
Cristina Peris-Martínez
Keyword(s):  
Central Corneal Thickness ◽  
Corneal Thickness ◽  
Mean Difference ◽  
The Other ◽  
Control Group ◽  
Healthy Population ◽  
Diagnostic Categories ◽  
Significant Difference ◽  
Biomechanical Parameters ◽  
The Mean

Purpose: To evaluate and compare corneal hysteresis (CH), corneal resistance factor (CRF), and central corneal thickness (CCT), measurements were taken between a healthy population (controls), patients diagnosed with glaucoma (DG), and glaucoma suspect patients due to ocular hypertension (OHT), family history of glaucoma (FHG), or glaucoma-like optic discs (GLD). Additionally, Goldmann-correlated intraocular pressure (IOPg) and corneal-compensated IOP (IOPcc) were compared between the different groups of patients. Methods: In this prospective analytical-observational study, a total of 1065 patients (one eye of each) were recruited to undergo Ocular Response Analyzer (ORA) testing, ultrasound pachymetry, and clinical examination. Corneal biomechanical parameters (CH, CRF), CCT, IOPg, and IOPcc were measured in the control group (n = 574) and the other groups: DG (n = 147), FHG (n = 78), GLD (n = 90), and OHT (n = 176). We performed a variance analysis (ANOVA) for all the dependent variables according to the different diagnostic categories with multiple comparisons to identify the differences between the diagnostic categories, deeming p < 0.05 as statistically significant. Results: The mean CH in the DG group (9.69 mmHg) was significantly lower compared to controls (10.75 mmHg; mean difference 1.05, p < 0.001), FHG (10.70 mmHg; mean difference 1.00, p < 0.05), GLD (10.63 mmHg; mean difference 0.93, p < 0.05) and OHT (10.54 mmHg; mean difference 0.84, p < 0.05). No glaucoma suspects (FHG, GLD, OHT groups) presented significant differences between themselves and the control group (p = 1.00). No statistically significant differences were found in the mean CRF between DG (11.18 mmHg) and the control group (10.75 mmHg; mean difference 0.42, p = 0.40). The FHG and OHT groups showed significantly higher mean CRF values (12.32 and 12.41 mmHg, respectively) than the DG group (11.18 mmHg), with mean differences of 1.13 (p < 0.05) and 1.22 (p < 0.001), respectively. No statistically significant differences were found in CCT in the analysis between DG (562 μ) and the other groups (control = 556 μ, FHG = 576 μ, GLD = 569 μ, OHT = 570 μ). The means of IOPg and IOPcc values were higher in the DG patient and suspect groups than in the control group, with statistically significant differences in all groups (p < 0.001). Conclusion: This study presents corneal biomechanical values (CH, CRF), CCT, IOPg, and IOPcc for diagnosed glaucoma patients, three suspected glaucoma groups, and a healthy population, using the ORA. Mean CH values were markedly lower in the DG group (diagnosed with glaucoma damage) compared to the other groups. No significant difference was found in CCT between the DG and control groups. Unexpectedly, CRF showed higher values in all groups than in the control group, but the difference was only statistically significant in the suspect groups (FHG, GLD, and OHT), not in the DG group.

scholarly journals Usefulness of the Non-Contact Tonometry in Out-Patient Screening

2016 ◽  
Vol 15 (2) ◽  
Author(s):  
Satheesh Solomon T Selvin ◽  
Chris Elsa Samson Jacob ◽  
Thomas Kuriakose
Keyword(s):  
Central Corneal Thickness ◽  
Care Center ◽  
Corneal Thickness ◽  
Tertiary Care ◽  
Cross Sectional Study ◽  
Applanation Tonometry ◽  
Cross Sectional ◽  
Significant Difference ◽  
Iop Measurement ◽  
The Mean

Purpose: Goldmann applanation tonometry (GAT) is considered the gold standard for Intraocular Pressure (IOP) measurement. It has the disadvantages of being a contact device, need for a slit-lamp, non-portability and need of a skilled examiner. Many hospitals are using a Non Contact Tonometry (NCT) as a screening device to save clinician time, however the usefulness is not proved in terms of reliability. This study was aimed to determine the usefulness of the Air-puff tonometer (TONOREF NIDEK II, NIDEK CO., LTD., JAPAN) over a GAT in a tertiary care center. Design: Cross-sectional Study Methods: This was a cross-sectional, non interventional observational study conducted on 224 eyes (right eye) from 224 patients. All patients underwent the IOP measurement with both methods and a central corneal thickness (CCT) measured. The data was analyzed using SPSS 20.0 software. Results: The mean age of the patients was 40.3±11.29 years. There was a statistically significant difference (p<0.001) between the mean NCT and GAT readings which persisted even after correction for central corneal thickness. The correlation between NCT and GAT using Pearson’s correlation coefficient was strong irrespective of the corrections for their corneal thickness (r = 0.751 and 0.718 for uncorrected and corrected values respectively). The correlation of the individual clinicians for the readings varied from moderate to strong. The ROC curve showed the best sensitivity and specificity to occur at around 13 to 14 mmHg. Conclusion: NCT seems to overestimate the IOP at low ranges as compared to the GAT and underestimate at higher ranges. The crossover of the values is seen between 12 to 13 mmHg.  The clinician should do an individualized analysis of his/her GAT measurements to the readings of the NCT machine at the clinic to obtain clinician specific nomogram. 

scholarly journals The pattern of central corneal thickness in patients attending a Tertiary Hospital in Dar-Es-Salaam

2021 ◽  
Vol 9 (2) ◽  
pp. 127-133
Author(s):  
Annamary Stanislaus ◽  
Ntsilane Susan Mosenene ◽  
Celina Mhina ◽  
John Stanslaus Kisimbi ◽  
Frederick Robert Burgess ◽  
...  
Keyword(s):  
Central Corneal Thickness ◽  
Corneal Thickness ◽  
Dar Es Salaam ◽  
Applanation Tonometry ◽  
P Value ◽  
Muhimbili National Hospital ◽  
National Hospital ◽  
Cross Sectional ◽  
Significant Difference ◽  
The Mean

Background: Central Corneal Thickness (CCT) is an indicator of corneal health status as well as being an essential tool in assessment and management of corneal diseases. It is an important factor in the diagnosis and management of glaucoma as it affects the measurement of intraocular pressure. However, the pattern of central corneal thickness in our population is not known. Our study aimed to describe the CCT measurements and their variation with age and sex among patients attending the eye clinic at Muhimbili National Hospital (MNH), in Dar es Salaam, Tanzania. Methodology: A hospital-based descriptive, cross-sectional study used convenient sampling to recruit adult patients aged 18 years and above, presenting to the MNH between August 2016 and January 2017.Visual acuity assessment, Goldman applanation tonometry and CCT assessment using an ultrasound pachymeter were performed. Patients with previous intraocular surgery were excluded. Results: A total of 398 patients (208 males and 190 females) were recruited. The mean CCT was 526.64±38.30 µm; being 523.99±38.20 µm for males and 529.7±38.3 µm for females. 226 (56.85%) had CCT of less than 520 µm.There was no statistically significant difference in CCT between gender. The proportion of patients with thinner CCT increased with increasing age from 25.8% in those < 30 years to 75% in those aged 71years and above. The mean CCT decreased with increasing age with P-value<0.001. Conclusion: The average CCT in patients attending Muhimbili National Hospital is 526.64 µm (SD 38.30) which is generally thin, inversely proportion to age and similar that of other Africans and African-Americans. This finding has implications for the management of glaucoma in this population.

Significance of dynamic contour tonometry in evaluation of progression of glaucoma in patients with a history of laser refractive surgery

2019 ◽  
Vol 104 (2) ◽  
pp. 276-281 ◽  
Author(s):  
Sang Yeop Lee ◽  
Eun Woo Kim ◽  
Wungrak Choi ◽  
Chan Keum Park ◽  
Sangah Kim ◽  
...  
Keyword(s):  
Refractive Surgery ◽  
Open Angle Glaucoma ◽  
Corneal Thickness ◽  
Significant Risk ◽  
Applanation Tonometry ◽  
Dynamic Contour Tonometry ◽  
Significant Difference ◽  
History Of ◽  
The Mean ◽  
Laser Refractive Surgery

AimsIn this study, we tested the hypothesis that intraocular pressure (IOP) parameters measured by dynamic contour tonometry (DCT) would be more relevant in progression of glaucoma when there is a history of laser refractive surgery (LRS) than the IOP parameters measured by Goldmann applanation tonometry (GAT) or calculated by correction formulae.MethodsNinety-eight eyes in 54 patients with open-angle glaucoma and a history of LRS were included in this retrospective study. IOP was measured by both GAT and DCT during follow-up. Baseline, mean, and peak IOP, IOP fluctuation, and IOP reduction were measured by each tonometry method. Corrected IOP parameters using central corneal thickness and mean keratometry values were also analysed. Clustered logistic regression was used to identify variables correlated with progression of glaucoma. Areas under the curve (AUCs) for correlated variables were also compared.ResultsThe mean DCT value (OR 1.36, p=0.024), peak DCT value (OR 1.19, p=0.02) and pattern SD (OR 1.10, p=0.016) were significant risk factors for progression. There was a significant difference in the predictive ability of the mean DCT and GAT values (AUC 0.63 and 0.514, respectively; p=0.01) and of the peak DCT and GAT values (0.646 and 0.503, respectively, p=0.009). The AUCs for corrected IOP did not exceed those of DCT.ConclusionsIOP measurements were more associated with progression of glaucoma when measurements were obtained by DCT than by GAT or correction formulae in eyes with a history of LRS.

Corneal biomechanical outcome of collagen cross-linking in keratoconic patients evaluated by Corvis ST

2020 ◽  
pp. 112067212094479
Author(s):  
Mahmoud Jabbarvand ◽  
Zahra Moravvej ◽  
Kianoush Shahraki ◽  
Hessam Hashemian ◽  
Hamed Ghasemi ◽  
...  
Keyword(s):  
Amplitude Ratio ◽  
Corneal Thickness ◽  
Case Series ◽  
Cross Linking ◽  
Corvis St ◽  
Significant Difference ◽  
Biomechanical Changes ◽  
The Mean ◽  
Prospective Case Series ◽  
Collagen Cross Linking

Purpose: A 6-month evaluation of the topographic and biomechanical changes induced by corneal collagen cross-linking (CXL) in keratoconic eyes using Pentacam and Corvis ST. Design: Longitudinal prospective case series. Methods: In this study, 67 eyes of 67 patients with progressive keratoconus (KCN) treated with “Epithelium-off” CXL were evaluated. Patients with stages 1 or 2 of KCN and a corneal thickness of at least 400 μm at the thinnest point were included. Standard ophthalmologic examinations were carried out for all patients. The topographic and biomechanical measurements of the cornea were obtained by Pentacam (Oculus Optikgeräte GmbH, Wetzlar, Germany) and Corvis ST (Oculus Optikgeräte GmbH, Wetzlar, Germany) preoperatively and 6-month postoperatively. Results: The mean age of the participants was 21.68 ± 4.23 years. There was significant difference in mean spherical equivalent (SE) before and 6 months after CXL. Uncorrected and best corrected visual acuity improved postoperatively, although not statistically significant. The mean and maximum keratometry showed a significant decrease 6 months after CXL (0.93 ± 0.38 D and 1.43 ± 0.62 D, respectively p < 0.001). Among Corvis ST parameters, first applanation length and velocity (AL1 and AV1) showed statistically significant changes. The radius at highest concavity changed significantly (0.13 ± 0.37 mm mean increase after CXL; p < 0.001). A significant increase was observed in stiffness parameter A1 (SP-A1; p < 0.001) and significant decreases were noted in integrated radius (IR) and deformation amplitude ratio (DAR; p < 0.001). Conclusion: Analyzing biomechanical changes after corneal cross-linking can provide basis for efficient KCN treatment. Corvis ST parameters demonstrated changes in corneal biomechanical characteristics indicative of stiffing after CXL.

scholarly journals ‘Comparison of Safety and Performance of Two Ophthalmic Viscosurgical Devices in Cataract Surgery’

2021 ◽  
Author(s):  
öznur işcan ◽  
Banu Torun Acar ◽  
Burcu Nurozler Tarakcı
Keyword(s):  
Endothelial Cell ◽  
Cataract Surgery ◽  
Corneal Thickness ◽  
Anterior Chamber Depth ◽  
Sodium Hyaluronate ◽  
Significant Difference ◽  
The Mean ◽  
Group 2 ◽  
And Performance ◽  
Group 1

Abstract Purpose: To compare the safety and performance of two ophthalmic viscosurgical devices (OVDs) Bio-Hyalur SV (Sodium Hyaluronate 3.0%) (Biotech Healthcare Group, Luzern, Switzerland) and Protectalon (sodium hyaluronate 2.0%) (VSY Biotechnology, Turkey) in cataract surgery. Methods: One hundred twenty eyes of one hundred twenty patients who underwent phacoemulsification surgery were included in the study. Postoperatively sixty eyes using Bio-Hyalur-SV were classified as Group 1, and sixty eyes using Protectalon as Group 2. Patients aged 45 and over, Grade I, II or III unilateral / double stained cataract, healthy eyes creating cataract inclueded in this study . Endothelial cell morphological parameters including endothelial cell density (ECD), cell number, cell area, coefficient of variation (CV) in cell size, cell hexagonality and central corneal thickness (CCT) were measured preoperatively and at postoperative first week, first and third month visits.Intraocular pressure (IOP) was measured with an applanation tonometer at every visit. Results: . There was a statistically significant decrease in the mean ECD all follow-up times when compared with the preoperative visit (p=0.000). In terms of mean ECD levels there was no significant difference between the two groups within three months postoperatively (p=0.616) In the first week after surgery, there was an significant increase in CCT in Group 1 and Group 2 respectively (p=0.000). The IOP was <23 mmHg in all of the patients on the first day after surgery. There was no significant difference in the incidence of IOP peaks between the two groups in every vizits. In both groups, a significant increase was observed in the mean IOP at first day, first week, and first month after surgery compared to preoperative values (p=0.000). But no significant difference in IOP increase in Group 1 (P=0.092), Group 2 (P=0.013) compared to preoperative values ​​at third month postoperatively (p <0.001 significant with Bonferrotti correction). Conclusion: The two OVD’s used in this study during cataract surgery were safe and effective. Both OVD’s resulted in similar rates of transient IOP increases and corneal endothelial damage also provided good anterior chamber depth and were fairly easy to remove.

Effect of Age on Individual Corneal Epithelial Thickness in Normal Eyes as Measured with Ultrasound Pachymeter

2021 ◽  
Vol 5 (1) ◽  
Keyword(s):  
Corneal Epithelium ◽  
Corneal Thickness ◽  
Age Groups ◽  
Age Group ◽  
Corneal Epithelial ◽  
Epithelial Thickness ◽  
Significant Difference ◽  
The Mean ◽  
Corneal Epithelial Thickness ◽  
Ultrasound Pachymeter

Purpose: The goal of this study was to determine age-relatedvariation in the thickness of the corneal epithelium using ultrasound pachymeter. Methods: One hundred three patients were enrolled in this study and grouped according to age: Group A (< 30 years), group B (31-40 years), group C (41-50 years), group D (51-60 years), group E (61-70), and group F (> 71). Total corneal and corneal epithelial thickness measurements were made using the SonogageCorneo-Gage Plus 2 (Cleveland, Ohio) ultrasound pachymeter. Correlations of central epithelial thickness with central total corneal thickness, age, and gender were calculated. In addition, mean central epithelial thickness (CET) was measured. One-way ANOVA testing and post hoc analysis with the Tukey test and Pearson correlation were performed to analyze data. Results: The mean epithelial thickness at the central cornea was 47.88±1.15 μm, with no statistically significant difference between right and left eyes, and no significant differences in gender or central total corneal thickness. The difference in mean epithelial thickness across age groups was statistically significant (p <0.008). The mean epithelial thickness of the > 71 years group was significantly thinner than that of the < 30 years, 31-40, 41-50, and 51-60 years age groups. Conclusions: Ultrasound pachymeter of the corneal epithelium demonstrated that the oldest age group (> 71 years) had significantly thinner central corneal epithelial thickness than the younger age groups. There was no correlation between epithelial thickness, total corneal thickness, gender, or laterality.

scholarly journals Evaluation of Optical Low Coherence Reflectometry Parameters in Patients with Exfoliation Syndrome

2015 ◽  
Vol 2015 ◽  
pp. 1-4
Author(s):  
Emrullah Beyazyıldız ◽  
Özlem Beyazyıldız ◽  
Süleyman Günaydın ◽  
Emrah Kan ◽  
Mert Şimşek ◽  
...  
Keyword(s):  
Healthy Subjects ◽  
Corneal Thickness ◽  
Anterior Chamber Depth ◽  
Exfoliation Syndrome ◽  
Low Coherence ◽  
Significant Difference ◽  
The Mean ◽  
Group 2 ◽  
Optical Low Coherence Reflectometry ◽  
Group 1

Purpose. To evaluate optical low coherence reflectometry (OLCR) parameters in patients with exfoliation syndrome (EXS) undergoing cataract surgery.Methods. Forty-seven eyes of 47 patients with EXS (Group 1), and 55 eyes of 55 healthy subjects (Group 2) were included in the study. Anterior chamber depth (ACD), lens thickness (LT), axial length (AL), central corneal thickness (CCT), horizontal corneal length (HCL), and pupil diameter (PD) parameters were measured by OLCR (Lenstar LS 900, Haag-Streit) and compared between groups. Shapiro-Wilk test and Mann WhitneyUtests were used for statistical analyses.Results. The mean ACD, HCL, and PD values were significantly lower in EXS group than in healthy subjects (P= 0.01,P= 0.04, andP<0.001, resp.). The mean LT was significantly higher in EXS group than in healthy subjects (P= 0.007). There was no significant difference between groups in means of AXL and CCT.Conclusions. According to OLCR measures, eyes with EXS have shallower ACD, smaller PD, thicker LT, shorter HCL, and no significantly different CCT levels.

Three-Dimensional Modeling and Computational Analysis of the Human Cornea Considering Distributed Collagen Fibril Orientations

2008 ◽  
Vol 130 (6) ◽  
Author(s):  
Anna Pandolfi ◽  
Gerhard A. Holzapfel
Keyword(s):  
Collagen Fibril ◽  
Mechanical Response ◽  
Corneal Thickness ◽  
Three Dimensional ◽  
Experimental Tests ◽  
Von Mises Stress ◽  
Fibrillar Structure ◽  
Material Structure ◽  
Human Cornea ◽  
Refractive Power

Experimental tests on human corneas reveal distinguished reinforcing collagen lamellar structures that may be well described by a structural constitutive model considering distributed collagen fibril orientations along the superior-inferior and the nasal-temporal meridians. A proper interplay between the material structure and the geometry guarantees the refractive function and defines the refractive properties of the cornea. We propose a three-dimensional computational model for the human cornea that is able to provide the refractive power by analyzing the structural mechanical response with the nonlinear regime and the effect the intraocular pressure has. For an assigned unloaded geometry we show how the distribution of the von Mises stress at the top surface of the cornea and through the corneal thickness and the refractive power depend on the material properties and the fibril dispersion. We conclude that a model for the human cornea must not disregard the peculiar collagen fibrillar structure, which equips the cornea with the unique biophysical, mechanical, and optical properties.

Evaluation of biometric parameters in phacomorphic glaucoma and mature cataracts

2020 ◽  
pp. 112067212091453
Author(s):  
Ali Keleş ◽  
Emine Şen ◽  
Ufuk Elgin
Keyword(s):  
Anterior Chamber ◽  
Axial Length ◽  
Odds Ratio ◽  
Central Corneal Thickness ◽  
Corneal Thickness ◽  
Anterior Chamber Depth ◽  
Mature Cataract ◽  
Biometric Parameters ◽  
Significant Difference ◽  
The Mean

Purpose: The aims of this study were to compare the biometric parameters and axial lengths of eyes with phacomorphic glaucoma and mature cataract and to identify differences that might predispose to development of phacomorphic glaucoma. Methods: Three hundred forty-two patients were enrolled in this retrospective study. The eyes were divided into four groups—Group (G)1: phacomorphic glaucoma ( n = 29), G2: mature cataract ( n = 313), G3: contralateral phacomorphic glaucoma ( n = 29), and G4: contralateral mature cataract ( n = 313). Central corneal thickness and anterior chamber depth were assessed by optical low-coherence reflectometry (Lenstar LS 900®; Haag-Streit AG, Switzerland), while axial length was determined by A-scan ultrasound biometry. Results: The mean central corneal thickness of G1 was significantly higher than in other groups ( p < 0.001) and the mean anterior chamber depth of G1 was the lowest among the groups ( p < 0.001). Also, G2 had lower mean anterior chamber depth than G4 ( p < 0.001) and G3 had lower mean anterior chamber depth than G4 ( p = 0.007). Anterior chamber depth less than 3.27 mm had the higher odds ratio for distinguishing G3 versus G4 (odds ratio = 10.79, p < 0.001). Furthermore, patients aged ⩾68.9 years had the higher odds ratio for distinguishing G1 versus G2 (odds ratio = 2.82, p = 0.019). There was no significant difference in the presence of pseudoexfoliation material between G1 and G2 ( p = 0.057). There were no significant differences in axial length values among the four groups ( p = 0.097). Conclusion: Advanced age and shallow anterior chamber depth were found to be risk factors for developing phacomorphic glaucoma, but the presence of pseudoexfoliation material was not found to play a role as a risk factor in phacomorphic glaucoma development.

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