Corneal Modulus and IOP Measurements in Canine Eyes Using Goldmann Applanation Tonometry and Tono-pen

Tang, Junhua; Pan, Xueliang; Weber, Paul A.; Liu, Jun

doi:10.1167/iovs.11-7407

Cited by 6 publications

(14 citation statements)

References 32 publications

(39 reference statements)

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“…45 Furthermore, the human corneal tensile modulus in strip extensiometry testing has been shown to be higher than that of canine corneas, with an average 1% strain secant modulus in human corneas of 2.44 MPa compared with 1.54 MPa in canine corneas. 46 This may result in a larger tangential strain in the canine cornea than in the human cornea for a similar IOP increase.…”

Section: Discussionmentioning

confidence: 99%

Spatially heterogeneous corneal mechanical responses before and after riboflavin–ultraviolet-A crosslinking

Palko

Tang

Perez

et al. 2014

Journal of Cataract and Refractive Surgery

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PURPOSE To determine the heterogeneous through-thickness strains in the cornea at physiologic intraocular pressures before and after corneal collagen crosslinking (CXL) using noninvasive ultrasound. SETTING Department of Biomedical Engineering, Ohio State University, Columbus, Ohio, USA. DESIGN Experimental study. METHODS Sixteen paired canine corneoscleral shells were divided into 2 groups. The CXL group completed a standard CXL protocol using riboflavin–ultraviolet-A (UVA) irradiation. The control group was given an identical treatment except UVA irradiation. Ultrasound scans (at 55 MHz) of the cornea were obtained before and after treatment as the corneoscleral shell was inflated from 5 mm Hg to 45 mm Hg to calculate the distributive through-thickness strains in the cornea. The mean radial and tangential strains of the whole cornea layer, as well as those of the anterior, middle, and posterior thirds of the cornea, were compared before and after treatment in the control group and CXL group using linear mixed models with repeated measures. RESULTS Significant reductions in tangential and radial strains occurred in the CXL group (P=.003 and P=.0025, respectively) but not the control group (P=.08 and P=.63, respectively). The anterior third had the smallest strains in all pretreated corneas (P<.001) and posttreated corneas (CXL group, P=.023; control group, P=.01). CONCLUSIONS Ultrasound speckle tracking showed heterogeneous strain distributions through the cornea and confirmed that CXL results in a stiffer corneal response (ie, smaller strains during physiologic loadings). This technique may provide a clinical tool to quantify the biomechanical effects of CXL. Financial Disclosure No author has a financial or proprietary interest in any material or method mentioned.

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Section: Discussionmentioning

confidence: 99%

Spatially heterogeneous corneal mechanical responses before and after riboflavin–ultraviolet-A crosslinking

Palko

Tang

Perez

et al. 2014

Journal of Cataract and Refractive Surgery

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“…The globes were cleaned carefully and a rectangular posterior strip adjacent to the ONH on the temporal side was dissected using a parallel blade excision device described in previous studies. 26,29 A representation of the scleral cutting position is seen in Figure 2.…”

Section: Mechanical Testingmentioning

confidence: 99%

Biomechanical Properties and Correlation With Collagen Solubility Profile in the Posterior Sclera of Canine Eyes With anADAMTS10Mutation

Palko

Iwabe

Pan

et al. 2013

Invest. Ophthalmol. Vis. Sci.

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Citation: Palko JR, Iwabe S, Pan X, Agarwal G, Komáromy AM, Liu J. Biomechanical properties and correlation with collagen solubility profile in the posterior sclera of canine eyes with an ADAMTS10 mutation. Invest Ophthalmol Vis Sci. 2013;54:268554: -269554: . DOI:10.1167 PURPOSE. We examined the biomechanical properties and correlation with the collagen solubility profile of the posterior sclera in a canine model of primary open-angle glaucoma caused by the G661R missense mutation in the ADAMTS10 gene. METHODS.Scleral strips from ADAMTS10-mutant (affected) dogs and age-matched controls were collected. Viscoelastic properties (i.e., complex modulus and tan[d]) were measured using dynamic mechanical analysis (DMA) with a 0.15% sinusoidal strain at different frequencies superimposed upon different preloads. A tensile ramp was performed following DMA. The collagen solubility profile was examined using a colorimetric hydroxyproline assay to determine the amount of soluble and insoluble collagen. The viscoelastic properties were compared between groups using linear mixed models for repeated measures at different preloads and frequencies. The correlation between the biomechanical properties and collagen content were evaluated using Pearson correlations. RESULTS.Complex modulus and tan(d) were significantly lower in the affected group (P < 0.001), and the differences were consistent at different preloads and frequencies. The B value from the tensile ramp test also was significantly lower in the affected group (P ¼ 0.02). The insoluble collagen was significantly lower in the affected group (P < 0.05) and correlated positively with the complex modulus (R ¼ 0.88, P < 0.005).CONCLUSIONS. An inherently weaker and biochemically distinct posterior sclera was observed in dogs with the G661R missense mutation in ADAMTS10 before clinical indications of optic nerve damage. It remains to be shown whether and how the altered scleral biomechanics may affect the rate of glaucoma progression following intraocular pressure elevation.

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“…18 The potential factors underlying this large underestimation were discussed in our previous publication. 8 Primarily, GAT is calibrated to the dimensions and properties of the human eye. After corneal stiffening through chemical cross-linking, GAT reading was increased to 15.6 mm Hg, considerably closer to the true pressure of (i.e., 15 mm Hg).…”

Section: Discussionmentioning

confidence: 99%

“…8,17,18 Briefly, the globe was placed in a holder padded with moistened gauze and affixed to a plastic plate that was mounted on the headset of a standard slit lamp (Topcon SL-2ED, Oakland, NJ). The IOP was controlled at 10, 15, 20, 30, and 40 mm Hg using a saline column and monitored by a pressure sensor that was connected to the anterior chamber.…”

Section: Gat and Tono-pen Measurementsmentioning

confidence: 99%

“…7 We have previously reported a correlation between GAT/ Tono-Pen (Reichert, Inc., Depew, NY) readings and corneal secant modulus measured by uniaxial tensile tests on canine corneas. 8 The purpose of the present study was to test the hypothesis that an altered corneal stiffness directly leads to a change in GAT and Tono-Pen readings. In addition, we explored the potential of using a noninvasive ultrasound method to obtain an estimate of corneal stiffness which may be used for correcting clinical measurements of tonometry.…”

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confidence: 98%

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Effect of Corneal Stiffening on Goldmann Applanation Tonometry and Tono-Pen Measurements in Canine Eyes

Tang¹,

Pan

Weber

et al. 2012

Invest. Ophthalmol. Vis. Sci.

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Corneal Modulus and IOP Measurements in Canine Eyes Using Goldmann Applanation Tonometry and Tono-pen

Cited by 6 publications

References 32 publications

Spatially heterogeneous corneal mechanical responses before and after riboflavin–ultraviolet-A crosslinking

Spatially heterogeneous corneal mechanical responses before and after riboflavin–ultraviolet-A crosslinking

Biomechanical Properties and Correlation With Collagen Solubility Profile in the Posterior Sclera of Canine Eyes With anADAMTS10Mutation

Effect of Corneal Stiffening on Goldmann Applanation Tonometry and Tono-Pen Measurements in Canine Eyes

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