Comparison of Goldmann Applanation Tonometry and Dynamic Contour Tonometry in Primary Open Angle Glaucoma

Abstract

Purpose: : To compare the measurements of intraocular pressure (IOP) as measured by Goldmann applanation tonometry (GAT) and dynamic contour tonometry (DCT) and to assess their dependence on central corneal thickness (CCT) in primary open angle glaucoma (OAG).

Methods: : In a prospective observational study, GAT and DCT were used, in a randomized order, to measure the IOP of 186 eyes in 93 OAG patients (mean age 65.5 (10.5); 58% female) participating in the Indianapolis Glaucoma Progression Study (IGPS). Immediately afterwards, CCT was measured using ultrasonic corneal pachymetry. Bland-Altman plots were used to evaluate the agreement between tonometers, and limits of agreement were determined. Multivariate regression analysis was used to evaluate the influence of CCT on IOP measurements obtained with both tonometers.

Results: : IOP values obtained by DCT and GAT were strongly correlated in all eyes (r=0.92; P<0.001). DCT measurements (mean ± SD, 18.3 ± 4.7 mm Hg) were significantly (P<0.001) higher than GAT measurements (mean ± SD, 16.6 ± 4.1 mm Hg). Measurements with GAT and DCT measurements were not correlated with CCT (GAT: r = 0.1025, P = 0.16, DCT: r = 0.05, P = 0.46).

Conclusions: : In OAG patients, IOP measurements by DCT and GAT revealed a strong correlation. Intraocular pressure measured by GAT was consistently lower when compared with DCT. GAT and DCT were not correlated with central corneal thickness.

Keywords: intraocular pressure • cornea: clinical science • cornea: basic science