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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Proponents of the closed stopcock dynamc claim greateraccuracy. The strongest correlationwas obtained in the range of 8 to 28 mm Hg with slopes of 0. A precise assessment of the IOP is usually most critical in clinicalsituations in which the pressure range is between 10 and 25 mm Hg.
The modeltreated cadavers and eyes nested within cadavers as random effects and didnot assume equal variability in the 3 devices. The ultrasonic CCT was measured after 15, 30,and 45 minutes of immersion. This study found a smaller intra- and interobserver variability for DCT 0.
Seven percent of patients were excluded from the analysis because of the inability to obtain good-quality DCT. Previous studies have shown IOP readings to decrease with successive GAT measurements, but this effect is absent in the case of rapid repetition of IOP measurements by the same examiner, as in the present study.
In contrast to GAT, for which the index on the scale is set at 2-mm increments to take into account the intra- and interobserver variability, DCT gives pressure readings with a precision of one decimal place. The patient was asked to blink before measurement to ensure equal distribution. Neither CCT, corneal curvature, corneal astigmatism, anterior chamber depth, nor axial length had a significant influence on pressure readings by DCT.
Dynamic contour tonometry: principle and use.
Even 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.
All measurements were taken by the same examiner in the following order: Goldmann applanation tonometry GAT has become the gold standard againstwhich other tonometers have been compared. Therefore, patients with normal-tension glaucoma may have a higher IOP than measured. Current Issue Archive Polls News. Comparisons in pressure measurements were performed using the nonparametric Wilcoxon signed ranks tonlmetry to account for the skewed and nonsymmetrical distribution of data points.
Other studies 68 – 10 found that patients with normal-tension glaucoma have thinner corneas than those of the general population.
The DCT showed no significant difference in accuracy withthe closed and open stopcock system, probably because the DCT displaces anegligible amount of fluid from the anterior chamber. The data also suggest that DCT isunaffected by the loss of the corneal epithelium in this model.
In a closed system, the cadaver globe is subject touncontrollable fluid leakage. Four eyes servedfor a preliminary study evaluating closed vs open stopcock systems, and theremaining 16 eyes were included in the main study and final analysis.
Glaucoma Today – Dynamic Contour Tonometry (March/April )
The examination technique with the DCT is similar to the technique used with the GAT, except that it does not require the sometimes cumbersome tuning of a knob to adjust two oscillating or melting semicircles, which leaves room for observer-dependent interpretation. After application of topical anesthesia to the cornea, a paper stripe impregnated with fluorescein was used to stain the precorneal tear film immediately before IOP measurement. Ophthalmologists are creating a pool of patients in whom a timely suspicion of glaucoma may be jeopardized by thinned or otherwise surgically altered corneas.
Furthermore, the corneas are subject tothinning even more during the dynamoc because of the dextran environmentand evaporation, perhaps explaining the consistently low GAT and PTG values. 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 interobserver cohtour, when measuring IOP in the same eye.
DCT seems to be an appropriate method of tonometry for routine clinical use.
PASCAL® Dynamic Contour Tonometer from Ziemer Group
Extreme care was taken with all penetrationsof the eye to avoid touching the endothelium, the iris, or the lens. In the absence of corneal epithelium, the usual fluoresceinhemirings cannot be detected.
Univariate linear regression using DCT as the dependent variable and GAT as the independent variable gives a slope of 0. Sign in to download free article PDFs Sign in to access your subscriptions Sign in to your personal account. Excluded were patients with pseudoexfoliation, a history of trauma, pigmentary dispersion, narrow or closed iridocorneal angle, evidence of any xynamic glaucoma, any type of preceding refractive surgery and corneal disease, and chronic or recurrent inflammatory eye disease eg, tknometry or uveitis.
Graefes Arch Clin Exp Ophthalmol. It is possible that this slight inaccuracy may be due tochanges in the corneal curvature as the pressure becomes very high. A separate analysis was runusing only the dyna,ic from trials with bottle heights from 10 to 30 cm mm Hg to derive the statistics for the “clinically significant” range.
Create a free personal account to download free article PDFs, sign up for alerts, customize your interests, and more. KaufmannNone; L.