Effect of central corneal thickness on dynamic contour tonometry and goldmann applanation tonometry in primary open-angle glaucoma

Objective: To compare the dependence of dynamic contour tonometry ( DCT) and Goldmann applanation tonometry ( GAT) on central corneal thickness ( CCT) in primary open-angle glaucoma. Methods: In a prospective study, the interocular ( right vs left eye) difference in intraocular pressure measured by DCT and GAT was compared with the interocular CCT difference in 125 patients with primary open-angle glaucoma. Results: Dynamic contour tonometry measurements ( mean +/- SD, 19.4 +/- 4.1 mm Hg) were significantly ( P = .004) higher than GAT measurements ( mean +/- SD, 15.5 +/- 3.4 mm Hg), correlating significantly with each other ( r(2) = 0.82, P < .001). The interocular difference in intraocular pressure correlated significantly with the interocular CCT difference for GAT ( r = 0.30, P = .001) and DCT ( r = 0.23, P = .02) readings. Dynamic contour tonometry and GAT intraocular pressure differences significantly increased with older age ( slope, 0.033 [ 95% confidence interval, 0.002-0.064] mm Hg/y; P = .03) but not with thicker CCT ( slope, 0.006 [ 95% confidence interval, -0.003 to 0.017] mm Hg/mu m; P = .22). Conclusions: In this series, GAT and DCT measurements were dependent on CCT in patients with primary open-angle glaucoma. Because intraocular pressure differences between DCT and GAT were independent of CCT, DCT and GAT are susceptible to similar measurement biases depending on CCT.