Comparison of Dynamic Contour Tonometry with Goldmann Applanation Tonometry

University of Zurich, Zürich, Zurich, Switzerland
Investigative Ophthalmology &amp Visual Science (Impact Factor: 3.4). 10/2004; 45(9):3118-21. DOI: 10.1167/iovs.04-0018
Source: PubMed

ABSTRACT The dynamic contour tonometer (DCT; Pascal tonometer) is a novel tonometer designed to measure intraocular pressure (IOP) independent of corneal properties. The purpose of this study was a comparison of the DCT with the Goldmann applanation tonometer (GAT) with respect to mean of IOP readings, the influence of ocular structural factors on IOP readings, and both intra- and interobserver variability, in a large group of healthy subjects.
In a prospective study of 228 eyes, IOP measurements by GAT and DCT were compared, and the effects of central corneal thickness (CCT), corneal curvature, axial length, and anterior chamber depth were analyzed. To evaluate intra- and interobserver variability, IOP was measured in eight eyes by four observers.
There was a high concordance between the IOP readings obtained by DCT and GAT. However, IOP readings were consistently higher with DCT than with GAT (median difference: +1.7 mm Hg, interquartile range [25th-75th percentile] = 0.8-2.7 mm Hg). 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. For repeated measurements the intraobserver variability was 0.65 mm Hg for the DCT and 1.1 mm Hg for the GAT (P = 0.008). Interobserver variability was 0.44 mm Hg for the DCT and 1.28 mm Hg for the GAT (P = 0.017).
IOP measurements by DCT are highly concordant with IOP readings obtained from GAT but do not vary in CCT and have a lower intra- and interobserver variability. DCT seems to be an appropriate method of tonometry for routine clinical use.

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Available from: Michael A Thiel, Nov 26, 2014
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    • "DCT is a method to measure IOP by using a pressure-sensitive tip that is closely shaped following the corneal curvature to minimize the corneal deformation. The forces of both sides of the cornea are meant to be nearly equal during the measurement.7 DCT measurements have been shown to be independent of structural changes of the cornea such as corneal edema or CCT.4,9–13,20,21 However, some authors describe that DCT is not completely independent from central corneal thickness or corneal edema.14,22–26 "
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    ABSTRACT: Intraocular pressure (IOP) determination using dynamic contour tonometry (DCT) has been considered to be independent of central corneal thickness (CCT), while Goldmann applanation tonometry (GAT) is known to be influenced by various corneal properties. In this study, IOP was measured before and 1 day after cataract surgery using GAT and DCT to investigate the possible effects of corneal edema on IOP measurements. Thirty patients with advanced cataracts were included in a pilot study. IOP was measured using GAT and DCT before and 1 day after phacoemulsification. CCT was determined before and after surgery to quantify postsurgical corneal edema. CCT increased significantly (by 89.7 ± 107.4 μm, P < 0.0001) 1 day after surgery. No significant difference was found for IOP measurements using GAT and DCT before surgery (mean IOP GAT: 17.5 ± 5.7 mmHg; mean IOP DCT: 17.9 ± 6.4 mmHg; P = 0.67) and 1 day after surgery (mean IOP GAT: 16.1 ± 6.6 mmHg; mean IOP DCT: 16.8 ± 8.3 mmHg; P = 0.69). IOP values using GAT and DCT were significantly correlated before as well as 1 day after surgery (before surgery: r = 0.82, P < 0.0001; after surgery r = 0.83, P < 0.0001). Bland-Altman plots showed a high variability in the difference in IOP measurements between methods before and 1 day after surgery. GAT and DCT seem to be equally valuable in IOP determination in postsurgical central corneal edema, although large differences between both methods are present in individual patients. IOP evaluation in corneal edema remains a difficult clinical challenge.
    Clinical ophthalmology (Auckland, N.Z.) 05/2013; 7:815-9. DOI:10.2147/OPTH.S44412
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    • "The increased corneal thickness in patients with DSAEK, however, does not affect IOP measurements by GAT as reported by Vajaranant et al. [55] and others [56]. Additional dynamic contour tonometry (DCT) and pneumotonometry which may measure IOP independent of corneal thickness, curvature, and hydration within certain ranges of IOP may be useful methods to measure IOP following DSAEK [57–60]. "
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    ABSTRACT: Glaucoma after corneal transplantation is a leading cause of ocular morbidity after penetrating keratoplasty. The incidence reported is highly variable and a number of etiologic factors have been identified. A number of treatment options are available; surgical intervention for IOP control is associated with a high incidence of graft failure. IOP elevation is less frequently seen following deep anterior lamellar keratoplasty. Descemet's striping-automated endothelial keratoplasty is also associated with postprocedure intraocular pressure elevation and secondary glaucoma and presents unique surgical challenges in patients with preexisting glaucoma surgeries. Glaucoma exists in up to three-quarters of patients who undergo keratoprosthesis surgery and the management if often challenging. The aim of this paper is to highlight the incidence, etiology, and management of glaucoma following different corneal transplant procedures. It also focuses on the challenges in the diagnosis of glaucoma and intraocular pressure monitoring in this group of patients.
    Journal of Ophthalmology 01/2012; 2012:576394. DOI:10.1155/2012/576394 · 1.43 Impact Factor
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    • "Similar results in nonglaucomatous subjects were found by other authors.22,24,25 Kaufmann et al reported lower IOP differences (1.7 mm on average) between the two methods by using a prototype of the Pascal tonometer in healthy volunteers.18 Kniestedt et al, performing manometry in cadaver eyes, showed that GAT IOPs were on average lower (by almost 4 mmHg) than DCT IOPs.44,45 "
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    ABSTRACT: To compare measurements obtained by Goldmann applanation tonometry (GAT) and Pascal dynamic contour tonometry (DCT), and to study their relationship to corneal thickness and biomechanical properties in nonglaucomatous eyes. This is a prospective and randomized study of 200 eyes from 200 non-glaucomatous subjects who underwent intraocular pressure (IOP) measurements by GAT and DCT. The two methods were compared and assessed for agreement by means of the Bland-Altman plot. Central corneal thickness (CCT) and corneal hysteresis (CH) were obtained by ultrasound pachymeter and Ocular Response Analyzer, respectively. The effect of CH and CCT was correlated with the DCT/GAT IOP differences. Mean age was 57.4 ± 14.7 years (range 24-82 years). Mean IOP measurements obtained were 16.7 ± 3.2 mmHg by GAT and 19.4 ± 3.3 mmHg by DCT. DCT showed a statistically significant higher mean IOP (2.7 ± 1.9 mmHg, P < 0.001) compared with GAT. Mean CCT and CH were 546.5 ± 40 μm and 10.85 ± 2.0 mmHg, respectively. The differences in IOP (DCT - GAT) were significantly correlated with CCT and CH (Pearson's correlation coefficient r = -0.517 and -0.355, P < 0.0001, respectively). The difference between the two correlation coefficients was statistically significant (P < 0.05, Z-statistic). According to the Bland-Altman plot, the results of the two methods were clinically different. Significantly higher IOP readings were obtained by DCT than by GAT in nonglaucomatous subjects. The IOP differences between the two methods were associated with CCT and CH, suggesting that DCT was less dependent on corneal parameters. Each method provides clinically different IOP values, indicating that DCT and GAT should not be used interchangeably.
    Clinical Ophthalmology 08/2011; 5:1071-7. DOI:10.2147/OPTH.S23086 · 0.76 Impact Factor
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