Corneal Parameters in Healthy Subjects Assessed by Corvis ST

Purpose: To evaluate corneal biomechanics using Corvis ST in healthy eyes from Iranian keratorefractive surgery candidates. Methods: In this prospective consecutive observational case series, the intraocular pressure (IOP), central corneal thickness (CCT), and biomechanical properties of 1,304 eyes from 652 patients were evaluated using Corvis ST. Keratometric readings and manifest refraction were also recorded. Results: The mean (±SD) age of participants was 28 ± 5 years, and 31.7% were male. The mean spherical equivalent refraction was –3.50 ± 1.57 diopters (D), the mean IOP was 16.8 ± 2.9 mmHg, and the mean CCT was 531 ± 31 μm for the right eye. The respective means (±SD) corneal biomechanical parameters of the right eye were as follows: first applanation time: 7.36 ± 0.39 milliseconds (ms); first applanation length: 1.82 ± 0.22 mm; velocity in: 0.12 ± 0.04 m/s; second applanation time: 20.13 ± 0.48 ms; second applanation length: 1.34 ± 0.55 mm; velocity out: –0.67 ± 0.17 m/s; total time: 16.84 ± 0.64 ms; deformation amplitude: 1.05 ± 0.10 mm; peak distance: 4.60 ± 1.01 mm; and concave radius of curvature: 7.35 ± 1.39 mm. In the linear regression analysis, IOP exhibited a statistically significant association with the first and second applanation times, total time, velocity in, peak distance, deformation amplitude, and concave radius of curvature. Conclusion: Our study results can be used as a reference for the interpretation of Corvis ST parameters in healthy refractive surgery candidates in the Iranian population. Our results confirmed that IOP is a major determinant of Corvis parameters.

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Detecting subclinical keratoconus by biomechanical analysis in tomographically regular keratoconus fellow eyes

European Journal of Ophthalmology ◽

10.1177/11206721211063740 ◽

2021 ◽

pp. 112067212110637

Author(s):

Victor A Augustin ◽

Hyeck-Soo Son ◽

Isabella Baur ◽

Ling Zhao ◽

Gerd U Auffarth ◽

...

Keyword(s):

Visual Acuity ◽

Central Corneal Thickness ◽

Corneal Thickness ◽

Case Series ◽

Biomechanical Analysis ◽

Corvis St ◽

Corrected Visual Acuity ◽

The Mean ◽

Best Corrected Visual Acuity ◽

Fellow Eyes

Purpose To analyze the tomographically non-affected second eyes of keratoconus patients using the Corvis ST to detect any biomechanical abnormalities or subclinical keratoconus. Methods In this retrospective, single-center, consecutive case series 244 eyes of 122 keratoconus patients were analyzed between November 2020 and February 2021. Fourteen fellow eyes fulfilled the inclusion criteria and showed no clinical or tomographic signs of keratoconus. Main outcome measures included best-corrected visual acuity, tomographic and biomechanical analyses using Scheimpflug imaging: Pentacam and Corvis ST (Oculus, Wetzlar, Germany). Tomographic analyses included anterior and posterior simulated keratometry, K-Max, central corneal thickness, thinnest corneal thickness, Belin/Ambrosio Ectasia Display, and the ABCD grading system. For biomechanical analyses, the corneal biomechanical index (CBI) and tomographic biomechanical index were used. Results The mean best-corrected visual acuity was 0.01 ± 0.10 logMAR. Mean K-Max was 43.79 ± 1.12 D, mean central corneal thickness 529 ± 25 µm, mean thinnest corneal thickness 524 ± 23 µm, and mean Belin/Ambrosio Ectasia Display 1.0 ± 0.32. The mean CBI was 0.30 ± 0.21. Regular CBI values were found in six of 14 patients. The mean tomographic biomechanical index was 0.47 ± 0.22 with regular values observed in only two of 14 patients. No signs of tomographic or biomechanical abnormalities were shown in only one of 14 keratoconus fellow eyes, with regular ABCD, Belin/Ambrosio Ectasia Display, CBI and tomographic biomechanical index values. Conclusions Tomographically normal fellow eyes of keratoconus patients are rare. In these cases, a biomechanical analysis of the cornea may help detect a subclinical keratoconus. The tomographic biomechanical index was the most sensitive index to verify a mild ectasia.

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

European Journal of Ophthalmology ◽

10.1177/1120672120944798 ◽

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.

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

Journal of Ophthalmology ◽

10.1155/2014/147516 ◽

2014 ◽

Vol 2014 ◽

pp. 1-8 ◽

Cited By ~ 46

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.

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Evaluation of the relation between myopia and central corneal thickness in patients admitted to vali-e-asr hospital in birjand, iran

Journal of Surgery and Trauma ◽

10.32592/jsurgery.2021.9.4.101 ◽

2021 ◽

pp. 138-143

Keyword(s):

Central Corneal Thickness ◽

Corneal Thickness ◽

Epidemiologic Study ◽

T Test ◽

P Value ◽

Study Results ◽

Significant Difference ◽

The Mean ◽

And Gender ◽

The Right

Introduction: Considering the increasing prevalence of myopia and the subsequent complications, and due to the dearth of studies on the correlation between myopia and gender with corneal thickness in Iran, this study aimed to determine this relationship in patients admitted to the ophthalmic clinic of Vali-e-Asr Hospital, Birjand, Iran. Methods: This descriptive-analytic epidemiologic study was conducted on 100 patients admitted to Vali-e-Asr ophthalmic clinic in Birjand, Iran, for one year since January 2017. According to the degree of myopia, the patients were divided into three groups of low (0-3 D), moderate (3-6 D), and high myopia (6≤D). Corneal thickness was measured using Orbscan and Pentacam. The data were analyzed in SPSS software (Version 19) through ANOVA and T-test to determine the possible relationship between myopia and central corneal thickness. A p-value equal to and less than (P≤0.05) was considered statistically significant. Results: Overall, 100 patients (49 males and 51 females) were enrolled in this study. Moderate myopia had the highest frequency in both eyes. The results of the T-test revealed that no significant difference was observed in the mean corneal thickness measured by Pentacam between the two genders (P=0.18 in the right eye and P=0.32 in the left eye). Based on the ANOVA findings, the mean corneal thickness measured by Pentacam was not significantly different among the myopia categories (P=0.05 in the right eye and P=0.51 in the left eye) Conclusions: The study results revealed that there was no significant relationship between myopia and gender with corneal thickness.

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Comparison of Corneal Biomechanical Properties between Post-LASIK Ectasia and Primary Keratoconus

Journal of Ophthalmology ◽

10.1155/2020/5291485 ◽

2020 ◽

Vol 2020 ◽

pp. 1-8

Author(s):

Wuxiao Zhao ◽

Yang Shen ◽

Weijun Jian ◽

Jianmin Shang ◽

Vishal Jhanji ◽

...

Keyword(s):

Linear Regression Analysis ◽

Corneal Thickness ◽

Case Series ◽

Biomechanical Properties ◽

Statistical Correlation ◽

Biomechanical Assessment ◽

Pearson's R ◽

Age Range ◽

Corneal Biomechanical Properties ◽

Pearson’S R

Purpose. To compare the corneal biomechanical properties between post-LASIK ectasia and primary keratoconus. Methods. A total of 42 eyes of 42 patients with matching age and central corneal thickness (CCT) were divided into two groups according to diagnosis of post-LASIK ectasia (PLE group; n = 21; age range: 22–47 years) and primary keratoconus (KC group; n = 21; age range: 21–47 years). The corneal biomechanical properties were assessed using Scheimpflug-based technology (Corvis ST; Oculus Optikgeräte, Wetzlar, Germany). The paired t-test and linear regression analysis were performed. Results. The PLE group had significantly higher mean stiffness parameter at the first applanation (SP-A1; 76.65 ± 21.66 vs 52.72 ± 13.65, p ≤ 0.001 ) and mean stress-strain index (SSI) (SSI: 0.78 ± 0.16 versus 0.64 ± 0.12, p = 0.001 ) than the KC group. SP-A1 was positively correlated with CCT in the PLE group (Pearson’s r = 0.816, p ≤ 0.001 ), but not in the KC group (Pearson’s r = −0.014, p = 0.952 ). No statistical correlation was observed between SSI and CCT in either group (Pearson’s r = 0.292, p = 0.199 , and Pearson’s r = 0.004, p = 0.985 , respectively). Conclusions. In our case series, KC manifested more severe than PLE in biomechanical properties. Since SSI measurements were independent of corneal thickness, it can be used for corneal biomechanical assessment.

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The influence of corneal density and thickness on tonometry measurement with goldmann applanation, non-contact and iCare tonometry methods

International Ophthalmology ◽

10.1007/s10792-022-02216-6 ◽

2022 ◽

Author(s):

Ahmed Lubbad ◽

Irene Oluwatoba-Popoola ◽

Melanie Haar ◽

Carsten Framme ◽

Anna Bajor

Keyword(s):

Linear Regression Analysis ◽

Corneal Thickness ◽

Biomechanical Properties ◽

Multiple Linear Regression Analysis ◽

Influential Factors ◽

Total Density ◽

Camera System ◽

System Data ◽

The Mean ◽

Mean Differences

Abstract Purpose To evaluate the effect of corneal density and thickness on the accuracy of tonometry readings obtained via three most used techniques. Method Intraocular pressures of 45 patients’ right eyes were measured using Goldmann Applanation, iCare, and non-contact tonometry methods. Corneal parameters were obtained using the Pentacam Camera System. Data obtained were analyzed using Paired t Test, Pearson’s correlation coefficient, multiple linear regression analysis, and Bland–Altman plots. Results The mean corneal thickness was 545.4 ± 3.93 μm. The mean corneal density of total, stromal, 0–2 mm, and 2–6 mm zones were 27.85 ± 6.23 GSU, 24.61 ± 6.05 GSU, 20.76 ± 2.96 GSU, and 20.81 ± 3.51 GSU respectively. IOP readings had a statistically significant correlation with corneal stromal thickness, as well as with total and stromal density. The stromal density, however, showed higher correlation with the three tonometry methods than did the total density (iCare: − .482 (0.001) stromal density versus− .464 (0.001) total density, NCT: − .376 (0.011) versus − .353 (0.017), GAT: − .306 (0.041) versus − .296 (0.048)). Statistical differences were found in comparing the iCare readings with GAT (P < 0,00) and with NCT (P < 0,00), with mean differences of 1.8 mmHg ± 2.6 and 2.0 mmHg ± 2.6 respectively. GAT and NCT measurements showed no statistical difference (P > 0.05). Conclusion This study shows that both central corneal thickness and stromal density are significant influential factors of reliable IOP readings. It is necessary to consider more corneal biomechanical properties, as well as exercise a high degree of caution in any new attempts towards adjusting an IOP-correction equation.

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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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The Role of Fine Needle Aspiration of Orbital Lesions: A Case Series

Acta Cytologica ◽

10.1159/000444385 ◽

2016 ◽

Vol 60 (1) ◽

pp. 31-38 ◽

Cited By ~ 6

Author(s):

Fabio Pagni ◽

Marta Jaconi ◽

Andrew James Smith ◽

Ambrogio Brenna ◽

Maria Gabriella Valente ◽

...

Keyword(s):

Case Series ◽

Needle Aspiration ◽

Lesion Size ◽

Fine Needle ◽

Computed Tomography Scans ◽

The Mean ◽

The Right ◽

First Time ◽

Orbital Lesions

Objective: This paper analyzes a series of ultrasound (US)-guided orbital fine needle aspirations (FNAs) which provide diagnostic information that cytopathologists approaching orbital lesions for the first time can find useful and underlines the importance of teamwork. Study Design: The investigators retrospectively obtained data from 24 consecutive orbital FNAs. For all patients, a complete clinicoradiological database was created. FNAs were performed under US guidance with 25-gauge needles and an aspiration biopsy syringe gun, and sent to the Department of Pathology for examination and data management. Results: The mean age of the patients was 54 years. Imaging studies included US, magnetic resonance imaging and computed tomography scans; 9 lesions involved the right orbit and 15 the left orbit. The mean lesion size was 23.6 ± 7.2 mm. After microscopic examination, 7 smears were labeled as ‘nondiagnostic', while in 17 cases a definitive diagnosis was proposed, which always proved to be correct (70.8%, specificity = 100%). Conclusions: The investigators believe that FNA biopsy of orbital masses is a necessary step; its weaknesses lie in the particularly delicate site of sampling and the extreme heterogeneity of lesions. Nevertheless, when orbital FNA is performed within a well-coordinated multidisciplinary team, it is a powerful tool that can be used to define the most appropriate management of these patients.

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