Clin Exp Ophthalmol. Dec;34(9) Dynamic contour tonometry: principle and use. Punjabi OS(1), Kniestedt C, Stamper RL, Lin SC. The PASCAL Dynamic Contour Tonometer (DCT) from Ziemer is a slitlamp mounted tonometer for measuring intraocular pressure IOP independent of corneal. The gold standard for assessing IOP is Goldmann applanation tonometry (GAT). Recently, the dynamic contour tonometer (DCT) has become.
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An important factor for the accuracy of IOP measurements is the variability that occurs between measurements performed by the same observer intraobserver or by different observers interobserverwhen measuring IOP in the same eye. Tonomefry when the eye-banked corneas were thinned post-mortem by photorefractive keratotomy or dehydration, DCT yielded readings very close to true IOP, whereas results with Goldmann applanation tonometry and pneumatonometry deteriorated further.
Mixed-effects models incorporated fixed and random effects. The pressure in the eye was then altered between 5 mm Hg and 58mm Hg.
PASCAL® Dynamic Contour Tonometer from Ziemer Group
Evidence from viewing position effects. Intraocular pressure measured using DCT was consistently higher compared with GAT measurements in human cadaver eyes, 19 in eyes undergoing refractive surgery, 2528 and in healthy eyes.
Invest Ophthalmol Vis Sci. Sign in to save your search Sign in to your personal account. You can manage this and all other alerts in My Account. Bayesian adaptive assessment of the reading function for vision: Since a value is given automatically by the strain gauge andthe automatic software in the base station, there is less chance for observerbias with this system than with GAT. No significant correlation could be found between the real IOPand the degree of error of any of the tonometers.
The concave surface of the tonometer tip matches the contour of the cornea; this contour matching creates equilibrium between capillary force, rigidity force, appositional force, and force exerted on the cornea by IOP. The so-called contour-matched tonometer tip has a concave surface that allows the cornea to assume the shape that it naturally assumes when pressure on both sides of the cornea is equal and distortion of the cornea is minimal.
Central corneal thickness as a risk factor for advanced glaucoma damage. BachmannNone; M. Further studies are warranted todetermine its reliability in patients and the effect of corneal thickness.
Furthermore, corneal shape radius and astigmatismelasticity, and rigidity differ widely among patients. Forcing thecentral area of the cornea into the contour of the DCT tip allows the examinerto measure the pressure of the eye directly and continuously on the externalsurface of the cornea. A piezoelectric pressure sensor 1 is built in the concavity of the tip. DCT seems to be an appropriate method of tonometry for routine clinical use.
Controversy exists regarding the method to manometrically measure IOPin cadaver eyes. Binocular motor coordination during saccades and fixations while reading: Further studies are indicated to further elucidate theproperties, usefulness, and accuracy of DCT in clinical situations.
Comparison of Dynamic Contour Tonometry with Goldmann Applanation Tonometry | IOVS | ARVO Journals
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Most nonpathologic corneas will be well within the scope of what DCT can handle correctly, fonometry. Proponents of the closed stopcock technique claim greateraccuracy. Some patients were unable to sit completely still, breathe quietly, and avoid slight movements of the eye or head. The pressure sensor contoug on the outside of the cornea thus measures a pressure that is equal to IOP.
First each independent variable was dynamci in a univariate analysis. Contour matching causes the cornea to assume a shape, which leaves it free of any bending forces and radial tension; the pressure is therefore equal on its inside and outside.
Dynamic Contour Tonometry
Scattergrams and linear regression were plotted for DCT, GAT, and PTGfor pressure values in the ranges 8 to 28, 8 to 38, and 8 to 58 mm Hg, respectively,in the hope of finding a linear tonomefry between corneal thickness andIOP values. Xynamic examination of dynammic reading fixations based on sentence corpus data.
Corneal thickness in ocular hypertension, primary open-angle glaucoma, and normal-tension glaucoma. Relationship between corneal thickness and measured intraocular pressure in a general ophthalmology clinic. Therefore, we cannot exclude that the use of eyedrops may have had an effect on corneal biomechanics and accordingly on IOP measurement.
Four eyes were used for the comparison of the open vs closed tubingsystems. However,in the dynajic eyes in which orbital topographic measurements were obtained, nosuch changes occurred in the anterior curvature. Purchase access Subscribe now. In these eyes, anterior cornealradius before the experiment at an IOP of approximately 20 mm Hg was 7.
Other tonometers, such as the pneumatonometer PTG2324 theMcKay-Marg tonometer, and its derivative, the handheld tonometer Tono-Pen;Mentor, Norwell, Masshave been reported to be more accurate, especiallyin corneas outside the average in thickness. In contrast to GAT, multivariable regression analysis showed no significant effect of corneal thickness, corneal curvature, astigmatism, anterior chamber depth, and axial length on DCT readings.