Comparisons between Pascal dynamic contour tonometry, the TonoPen, and Goldmann applanation tonometry in patients with glaucoma

Abstract

ABSTRACT.Purpose: To compare intraocular pressure (IOP) measurements taken with Pascal dynamic contour tonometry (DCT), the TonoPen and the Goldmann applanation tonometry (GAT). The influence of central corneal thickness (CCT) on IOP measurements taken with Pascal DCT and the TonoPen was evaluated.Methods: One eye in each of 101 consecutive patients with primary open-angle glaucoma (POAG) underwent ultrasonic CCT measurement and IOP evaluation with GAT, Pascal DCT and the TonoPen in random order. The agreement between results from Pascal DCT and the TonoPen and those of GAT was assessed using the Bland)Altman method. The deviation of Pascal DCT and TonoPen readings from GAT values, corrected for CCT, was calculated and correlated to CCT using a linear regression model. Results:The mean of the differences in IOP measurements was 3.2 ± 2.4 mmHg for Pascal DCT minus GAT readings and 0.5 ± 4.5 mmHg for TonoPen minus GAT readings. The 95% confidence interval of differences in IOP measurements was higher between TonoPen and GAT readings () 6 to 7 mmHg) than between Pascal and GAT readings (0.1)6.8 mmHg). Pascal DCT significantly overestimated IOP compared with GAT, especially for higher IOP readings. Bland)Altman scatterplots showed reasonable inter-method agreement between Pascal DCT and GAT measurements, and poor agreement between TonoPen and GAT measurements. The deviations of Pascal DCT and TonoPen readings from the corrected GAT values were both highly correlated with CCT values (linear regression analysis, p < 0.0001). The mean change in measured IOP for a 10-lm increase in CCT was 0.48 mmHg for Pascal DCT and 0.74 mmHg for the TonoPen.Conclusions: Agreement with GAT measurements was higher for Pascal DCT than for TonoPen readings; however, Pascal DCT significantly overestimated IOP values compared with GAT. Measurements of IOP obtained with both Pascal DCT and the TonoPen appeared to be influenced by CCT, and this influence appeared to be greater for the latter.

Influence of age, central corneal thickness, and quality score on dynamic contour tonometry

“…This value appears greater than those reported previously, which varied between 0.94 and 2 mmHg. 11,12,16,17 The tendency of DCT to give higher IOP readings compared with GAT is in good agreement with the results of a recently published study, which demonstrated that the IOP measured by applanation tonometry was 1.2-2 mmHg lower than the IOP measured manometrically in human in vivo eyes. 18 The higher readings obtained with DCT may be expected, as DCT was calibrated against a manometrically controlled standard pressure rather than a GAT pressure reading.…”

“…As previously shown by Salvetat et al, 16 our study showed that neither DCT nor GAT IOP readings were correlated with age. Interestingly, Kotecha et al 26 found that GATÀDCT differences were positively associated with age.…”

Current Concepts in the Diagnosis of Primary Open Angle Glaucoma

“…35 However, its accuracy has been questioned in eyes with abnormal central corneal thickness and structural rigidity, and in those that have undergone corneal ablation with laser refractive surgery. 35 Goldmann applanation tonometry was calibrated for a CCT of 520µm, and it underestimates IOP in eyes with thin corneas and overestimates IOP in eyes with thick corneas, with several clinical implications. 35 The Pascal dynamic contour tonometer (DCT) is a novel device designed for IOP measurements assumed to be largely independent on CCT and corneal curvature.…”

“…35 Goldmann applanation tonometry was calibrated for a CCT of 520µm, and it underestimates IOP in eyes with thin corneas and overestimates IOP in eyes with thick corneas, with several clinical implications. 35 The Pascal dynamic contour tonometer (DCT) is a novel device designed for IOP measurements assumed to be largely independent on CCT and corneal curvature. 35 When Goldmann applanation tonometer was compared with the TonoPen and DCT, agreement with GAT measurements was higher for Pascal DCT than for TonoPen readings; however, Pascal DCT significantly overestimated IOP values compared with GAT.…”

“…35 The Pascal dynamic contour tonometer (DCT) is a novel device designed for IOP measurements assumed to be largely independent on CCT and corneal curvature. 35 When Goldmann applanation tonometer was compared with the TonoPen and DCT, agreement with GAT measurements was higher for Pascal DCT than for TonoPen readings; however, Pascal DCT significantly overestimated IOP values compared with GAT. 35 Measurements of IOP obtained with both Pascal DCT and the TonoPen appeared to be influenced by CCT, and this influence appeared to be greater for the latter.…”