Comparison of dynamic contour tonometry and Goldmann applanation tonometry in relation to central corneal thickness in primary congenital glaucoma

Abstract

To compare intraocular pressure (IOP) measurements obtained with dynamic contour tonometer (DCT) and Goldmann applanation tonometer (GAT), and to investigate their relationship to central corneal thickness (CCT) in primary congenital glaucoma (PCG) eyes. Thirty-one eyes of 31 PCG patients (25.7 ± 7.2 years old) were examined. PCG was defined as elevated IOP, enlarged corneal diameter (buphthalmos), Haab's striae and abnormal findings at gonioscopy. The mean of three measurements of GAT, DCT (quality scores 1 and 2), and CCT were obtained and assessed for agreement by means of Bland-Altman plot and for Spearman correlation test. Mean CCT was 534 ± 72.3 μm (range: 430 to 610 μm). Mean IOP measurements were 15.1 ± 4.2 mmHg (range: 5.5 to 22.7 mmHg) for DCT and 14.5 ± 5.6 mmHg (range: 7.0 to 34.0 mmHg) for GAT (P = 0.244). Spearman correlation tests showed that IOP difference (DCT - GAT) was not correlated with CCT (r (2) = 0.023, P = 0.417). IOP measurements by DCT were weakly but statistically correlated with those obtained with GAT (r(2) = 0.213, P = 0.0089). Bland-Altman analysis revealed poor agreement between DCT and GAT readings, considering the 95 % confidence intervals of ± 10.45 mmHg. The differences between DCT and GAT readings were not influenced by CCT in this series of patients. Considering the weak correlation and the poor agreement observed between GAT and DCT measurements and that they both may be affected by corneal biomechanical changes, these methods should not be used interchangeably, and may possibly give no meaningful IOP values in PCG patients.