Comparison of Goldmann and Pascal tonometry in relation to corneal hysteresis and central corneal thickness in nonglaucomatous eyes

Abstract

Objective: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.Methods: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.Results: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.Conclusion: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.

Secondary Glaucoma After Intravitreal Dexamethasone 0.7 mg Implant in Patients with Retinal Vein Occlusion: A One-Year Follow-Up

“…In contrast to GAT, the Pascal tonometry provides direct transcorneal IOP measurements independent of central corneal thickness, corneal curvature, and is less prone to examiner dependant measurement bias. [11][12][13][14][15] As expected, Pascal readings in our study were in mean 2-4 mmHg higher than GAT readings. [16][17][18][19] However, even after correcting for this well described fact, Pascal readings detected IOP elevations more sensitive, especially at IOP values ‡ 25 mmHg Similar to the results of the GENEVA study, we found a peak of IOP elevation 2 months after dexamethasone 0.7 mg injections.…”

Corneal Hysteresis as a Risk Factor for Glaucoma Progression: A Prospective Longitudinal Study

“…38 However, other studies have described a weak but significant relationship between GAT IOP and CH and this could confound the determination of the independent role of CH as a risk factor for progression. 39, 4042 It should be noted, however, that even though part of the predictive effect of CH might be explained by its effect on GAT measurements, CH would still be a valid and relevant predictive factor, as shown by the model presented in our study. Further studies should clarify the role of CH as a true independent risk factor for glaucoma progression by evaluating its role in multivariable models including cornealindependent IOP measurements.…”

Correlation between ocular perfusion pressure and ocular pulse amplitude in glaucoma, ocular hypertension, and normal eyes

“…DCT is an alternative way to measure IOP, and is based on a completely new physical principle that does not distort the corneal anatomy 16. Therefore, DCT seems to be less affected by factors such as corneal thickness and hysteresis when compared with GAT 25. In our study, the difference between mean measurements taken on DCT and GAT was 1.7 mmHg.…”