Corneal Deformation Parameters Provided by the Corvis-ST Pachy-Tonometer in Healthy Subjects and Glaucoma Patients

Salvetat, Maria Letizia; Zeppieri, Marco; Tosoni, Claudia; Felletti, Mirella; Grasso, Leonardo; Brusini, Paolo

doi:10.1097/ijg.0000000000000133

Cited by 89 publications

(106 citation statements)

References 28 publications

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“…[5][6][7]10,[14][15][16][17][18][19][20]29,32,33 Other studies have found that other baseline factors such as axial length, 21,23 age, 27 and CCT 23 also are significantly associated with corneal biomechanical parameters. To accurately understand the relationship between corneal biomechanics and ocular diseases, the effect of baseline factors on corneal deformation parameters must be clarified.…”

Section: Discussionmentioning

confidence: 99%

“…This device measures a variety of parameters such as length, area, radius, arc length, and velocity of the corneal deformation at several defined time points. Previous studies have reported significant differences between the values of the corneal deformation parameters measured with the Corvis ST in normal eyes and those in eyes with glaucoma [13][14][15][16] and keratoconus 17 and after refractive 11,18,19 and keratoplasty surgeries, 20 suggesting the potential clinical relevance of the dynamic Scheimpflug analyzer to those conditions. In addition to ocular pathologies, the corneal biomechanical parameters are associated with a range of ocular and systemic factors.…”

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confidence: 99%

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Factors Associated With Corneal Deformation Responses Measured With a Dynamic Scheimpflug Analyzer

Miki

Maeda

Ikuno

et al. 2017

Invest. Ophthalmol. Vis. Sci.

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PURPOSE. The purpose of this study was to clarify correlations between corneal deformation parameters measured with a dynamic Scheimpflug analyzer and baseline factors such as axial length, intraocular pressure (IOP), age, central corneal thickness (CCT), and corneal curvature.METHODS. Ninety-six eyes of 96 healthy subjects (mean 55.2 6 16.1 years of age) were examined using a dynamic Scheimpflug analyzer. Eighteen of 35 deformation parameters were selected for analyses based on measurement reliability and clinical relevance. The associations between corneal deformation parameters and axial length, IOP, age, CCT, and average corneal power were evaluated using multivariate regression analyses.RESULTS. Deformation parameters were correlated significantly with axial length (n ¼ 13), IOP (n ¼ 13), age (n ¼ 8), and CCT (n ¼ 6) in the multivariate models. Longer axial length corresponded with greater corneal deformability, less viscous damping, and less movement of the entire eye. Higher IOP was associated with greater corneal resistance and less movement of the entire eye. Older age was associated with less corneal deformability and greater movement of the entire eye. Corneal curvature was correlated significantly with only three deformation parameters.CONCLUSIONS. This study clarified the substantial impact of axial length, age, and IOP on the biomechanical responses of the cornea and the entire eye. In contrast, corneal curvature did not affect most of the deformation parameters. The current results confirmed the importance of corneal biomechanics, especially in eyes with longer axial length and in older subjects.

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Factors Associated With Corneal Deformation Responses Measured With a Dynamic Scheimpflug Analyzer

Miki

Maeda

Ikuno

et al. 2017

Invest. Ophthalmol. Vis. Sci.

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“…16 Several articles have recently been published on the possible applications of the Corvis ST, particularly evaluating possible biomechanical differences in the cornea after undergoing refractive surgery procedures, [17][18][19][20][21][22] between normal and keratoconic patients, [23][24][25][26] after cross-linking, 27 and in patients with glaucoma. [28][29][30][31] However, it has been demonstrated that IOP and pachymetry have important influences on most corneal biomechanical metrics provided by both the Corvis ST and ORA. [32][33][34] It is therefore relevant to investigate the distribution and normal limits for the in vivo corneal biomechanical data derived from dynamic corneal response parameters, and determine whether these metrics have correlations with IOP and corneal thickness.…”

Section: Resultsmentioning

confidence: 99%

Influence of Pachymetry and Intraocular Pressure on Dynamic Corneal Response Parameters in Healthy Patients

et al. 2016

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n 1619, Scheiner provided the first precise description of the corneal shape using glass balls of known curvatures.1 From that first description, many other diagnostic tools have been developed to describe corneal shape, from keratometry to corneal topography (front surface curvature maps), 2 then into three-dimensional corneal tomography systems.3 More recently, it has been shown that corneal biomechanical behavior plays an important role in maintaining corneal shape, which is necessary for light refraction and clear vision, 4 and should therefore be considered in understanding the development of ectatic diseases 5,6 and the results of surgery. 4,7 Until recently, the evaluation of corneal biomechanical properties had been restricted to ex vivo laboratory studies 5,8 and mathematical corneal models. METHODS: Seven hundred five healthy patients were included in this multicenter retrospective study. The biomechanical response data were analyzed to obtain normative values with their dependence on corrected and clinically validated intraocular pressure estimates developed using the finite element method (bIOP), central corneal thickness (CCT), and age, and to evaluate the influence of bIOP, CCT, and age. RESULTS:The results showed that all DCRs were correlated with bIOP except deflection amplitude (DefA) ratio, highest concavity (HC) radius, and inverse concave radius. The analysis of the relationship of DCRs with CCT indicated that HC radius, inverse concave radius, deformation amplitude (DA) ratio, and DefA ratio were correlated with CCT (rho values of 0.343, -0.407, -0.444, and -0.406, respectively). The age group subanalysis revealed that primarily whole eye movement followed by DA ratio and inverse concave radius were the parameters that were most influenced by age. Finally, custom software was created to compare normative values to imported examinations.CONCLUSIONS: HC radius, inverse concave radius, DA ratio, and DefA ratio were shown to be suitable parameters to evaluate in vivo corneal biomechanics due to their independence from IOP and their correlation with pachymetry and age. The creation of normative values allows the interpretation of an abnormal examination without the need to match every case with another normal patient matched for CCT and IOP.[J Refract Surg. 2016;32(8):550-561.]

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“…Some previously reported CST-IOP measurements were higher than the GAT-IOP measurements [7–10] and other studies reported that the CST-IOP was similar to [11] or was lower than [12] the GAT-IOP. Previous comparisons between the CST-IOP and GAT-IOP were controversial [7–12].…”

Section: Discussionmentioning

confidence: 96%

A Comparison of the Corrected Intraocular Pressure Obtained by the Corvis ST and Reichert 7CR Tonometers in Glaucoma Patients

2017

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The purpose of the study was to investigate the accuracy of two corrected intraocular pressure (IOP) measurements by Corvis Scheimpflug Technology (CST)-IOPpachy and by corneal-compensated IOP (IOPcc) using the Reichert 7CR (7CR) tonometers. We also investigated the effects of corneal anatomical and structural parameters on the IOP measurements. The participants included 90 primary open-angle glaucoma patients. We assessed the IOP measurements, obtained by the CST, 7CR, and Goldmann applanation tonometer (GAT), using a paired t-test with Bonferroni correction, Bland-Altman plots, and multiple regression analyses. The 7CR-IOPcc gave the highest value (15.5 ± 2.7 mmHg), followed by the 7CR-IOPg (13.7 ± 3.1 mmHg), GAT-IOP (13.6 ± 2.2 mmHg), CST-IOP (10.3 ± 2.6 mmHg), and CST-IOPpachy (9.7 ± 2.5 mmHg). The values of CST-IOPpachy were significantly lower than those obtained by the other IOP measurement methods (all, p < 0.01). The values of 7CR-IOPcc were significantly higher than those obtained by the other IOP measurement methods (all, p < 0.01). Bland-Altman plots showed a mean difference between the GAT-IOP and the other IOP measurements (CST-IOP, CST-IOPpachy, 7CR-IOPg, and 7CR-IOPcc), which were −3.20, −3.82, 0.14, and 2.00 mmHg, respectively. The widths of the 95% limits of agreement between all pairs of IOP measurements were greater than 3 mmHg. With the exception of the 7CR-IOPcc, all of the IOP variations were explained by regression coefficients involving gender, average corneal curvature, and central corneal thickness. The IOP values obtained by the GAT, CST, and 7CR were not interchangeable. Each new IOP measurement device that was corrected for ocular structure had its own limitations.

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Corneal Deformation Parameters Provided by the Corvis-ST Pachy-Tonometer in Healthy Subjects and Glaucoma Patients

Cited by 89 publications

References 28 publications

Factors Associated With Corneal Deformation Responses Measured With a Dynamic Scheimpflug Analyzer

Factors Associated With Corneal Deformation Responses Measured With a Dynamic Scheimpflug Analyzer

Influence of Pachymetry and Intraocular Pressure on Dynamic Corneal Response Parameters in Healthy Patients

A Comparison of the Corrected Intraocular Pressure Obtained by the Corvis ST and Reichert 7CR Tonometers in Glaucoma Patients

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