Open source software for the analysis of corneal deformation parameters on the images from the Corvis tonometer

Koprowski, Robert

doi:10.1186/s12938-015-0027-3

Cited by 10 publications

(1 citation statement)

References 32 publications

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“…By using the ultra-high-speed Scheimpflug camera, CST provides much more information than ORA. 12 Both of them are noncontact tonometers that applanate cornea by air puff. The difference is that CST uses a high-speed Scheimpflug camera which takes cross-sectional images of the cornea during deformation process.…”

Section: Introductionmentioning

confidence: 99%

Keratoconus diagnosis using Corvis ST measured biomechanical parameters

Elham

Jafarzadehpur

Hashemi

et al. 2017

Journal of Current Ophthalmology

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PurposeTo assess the diagnostic power of the Corneal Visualization Scheimpflug Technology (Corvis ST) provided corneal biomechanical parameters in keratoconic corneas.MethodsThe following biomechanical parameters of 48 keratoconic eyes were compared with the corresponding ones in 50 normal eyes: time of the first applanation and time from start to the second applanation [applanation-1 time (A1T) and applanation-2 time (A2T)], time of the highest corneal displacement [highest concavity time (HCT)], magnitude of the displacement [highest concavity deformation amplitude (HCDA)], the length of the flattened segment in the applanations [first applanation length (A1L) and second applanation length (A2L)], velocity of corneal movement during applanations [applanation-1 velocity (A1V) and applanation-2 velocity (A2V)], distance between bending points of the cornea at the highest concavity [highest concavity peak distance (HCPD)], central concave curvature at the highest concavity [highest concavity radius (HCR)]. To assess the change of parameters by disease severity, the keratoconus group was divided into two subgroups, and their biomechanical parameters were compared with each other and with normal group. The parameters' predictive ability was assessed by receiver operating characteristic (ROC) curves. To control the effect of central corneal thickness (CCT) difference between the two groups, two subgroups with similar CCT were selected, and the analyses were repeated.ResultsOf the 10 parameters compared, the means of the 8 were significantly different between groups (P < 0.05). Means of the parameters did not show significant difference between keratoconus subgroups (P > 0.05). ROC curve analyses showed excellent distinguishing ability for A1T and HCR [area under the curve (AUC) > 0.9], and good distinguishing ability for A2T, A2V, and HCDA (0.9 > AUC > 0.7). A1T reading was able to correctly identify at least 93% of eyes with keratoconus (cut-off point 7.03). In two CCT matched subgroups, A1T showed an excellent distinguishing ability again.ConclusionsThe A1T seems a valuable parameter in the diagnosis of keratoconic eyes. It showed excellent diagnostic ability even when controlled for CCT. None of the parameters were reliable index for keratoconus staging.

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Section: Introductionmentioning

confidence: 99%

Keratoconus diagnosis using Corvis ST measured biomechanical parameters

Elham

Jafarzadehpur

Hashemi

et al. 2017

Journal of Current Ophthalmology

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In vivo human corneal deformation analysis with a Scheimpflug camera, a critical review

Lanza¹,

Iaccarino²,

Bifani³

2016

Journal of Biophotonics

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Corneal morphological analysis has greatly improved in recent years, providing physicians with new and reliable parameters to study. Moreover, today corneal functional too is a routine analysis, thanks to biomechanical evaluation allowed by an ocular response analyzer (Reichert Ophthalmic Instrument, Depew, NY, USA). Corvis ST (OCULUS Optikgeräte GmbH, Wetzlar, Germany), that relies on the ultrahigh speed Scheimpflug camera, is a new device providing corneal deformation parameters measured ny scanning the cornea response to an air puff; it is an instrument able to measure intraocular pressure too. This device could open up a whole new prospective in screening, detecting and managing corneal diseases, intraocular pressure measurement and in evaluating surgical procedures involving the cornea. This paper provides a comprehensive explanation of Corvis ST measurement principles and parameters and a literature review of scientific studies.

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Determining in vivo elasticity and viscosity with dynamic Scheimpflug imaging analysis in keratoconic and healthy eyes

Wang

Tian

Zheng

2016

Journal of Biophotonics

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The paper presents a novel analysis method of corneal elasticity and viscosity based on corneal visualization Scheimpflug technology (CorVis ST) for keratoconus diagnosis. Methods for air puff force measurement and corneal imaging boundary extraction were proposed. Corneal biomechanical properties, described as tangent stiffness coefficient (STSC ) and energy absorbed area (Aabsorbed ), were assessed using the curves of the applied air puff force with corneal displacement to form a loading-unloading cycle. Twenty-five patients with keratoconus and 34 healthy control subjects, matched for intraocular pressure (IOP), were enrolled in this prospective study. The results showed that the intraclass correlation coefficients (ICC) of the STSC and Aabsorbed were 0.941 and 0.878 in Healthy group; and were 0.891 and 0.809 in Keratoconus group, respectively. Both STSC and Aabsorbed of keratoconus patients were significantly different from that of controls (both probability value P< 0.001). ROC curve analysis showed that the area under curve for STSC was 0.918 and for Aabsorbed was 0.894, which reached a good level of predictive accuracy for detecting keratoconus. Our results demonstrated that this new analysis method could be used to characterize the biomechanical properties of corneas. (a) The air puff force of CorVis ST was measured by a custom-designed force detection system. (b) Corneal displacement was extracted from CorVis ST using a proposed imaging analysis. (c) With the utilization of the air puff force and corneal dynamic displacement, an analysis method was developed to introduce new corneal biomechanical parameters - STSC and Aabsorbed .

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Open source software for the analysis of corneal deformation parameters on the images from the Corvis tonometer

Cited by 10 publications

References 32 publications

Keratoconus diagnosis using Corvis ST measured biomechanical parameters

Keratoconus diagnosis using Corvis ST measured biomechanical parameters

In vivo human corneal deformation analysis with a Scheimpflug camera, a critical review

Determining in vivo elasticity and viscosity with dynamic Scheimpflug imaging analysis in keratoconic and healthy eyes

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