Comparison of Goldmann applanation tonometry and dynamic contour tonometry in healthy and glaucomatous eyes

To compare the measurements of intraocular pressure (IOP) with dynamic contour tonometry (DCT) and Goldmann applanation tonometry (GAT) in healthy and glaucomatous eyes and to evaluate the influence of corneal thickness (CCT), corneal curvature (CC), axial length (AL), and age on these tonometric alternatives.

Three hundred eyes of 100 healthy subjects, 100 patients with primary open angle glaucoma, and 100 patients with primary angle-closure glaucoma underwent IOP evaluation with DCT and GAT, and measurements of CCT, CC, and AL. Bland-Altman plots were used to evaluate the agreement between tonometers. Regression analysis was used to evaluate the influence of ocular structural factors on IOP measurements obtained with both tonometers.

Bland-Altman plots indicated that the 95% limits of agreement between tonometers were -1.4 to 6.6 mmHg. DCT values measured 2.6+/-1.9 mmHg higher than GAT readings (P<0.001). The mean IOP difference between DCT and GAT (DeltaIOP) was higher in healthy than in glaucomatous eyes and the magnitude of difference increased with increasing CCT. A significant reduction of DeltaIOP with an increase in both CCT (P<0.001) and IOP values (P<0.001) was found. Regression analysis showed no effect of CC, AL, and age on both DCT and GAT readings. In contrast to GAT (P<0.001), DCT measurements were not influenced by CCT (P=0.43).

IOP readings obtained by DCT were higher and less affected by CCT than those by GAT. The DeltaIOP was higher in healthy than in glaucomatous eyes and decreased in relation to increased CCT and IOP values.