Assessment of Factors Affecting the Difference in Intraocular Pressure Measurements Between Dynamic Contour Tonometry and Goldmann Applanation Tonometry

Purpose: To determine if the difference in intraocular pressure (IOP) measurements between dynamic contour tonometry (DCT) and Goldmann applanation tonometry (GAT) is correlated with axial length (AL), and to assess the possible influence of age, sex, central corneal thickness (CCT), corneal hysteresis (CH), ocular pulse amplitude (OPA), and glaucoma status on the difference in IOP measurements between the 2 instruments (Delta IOP=DCT(IOP)-GAT(IOP)). Methods: Two hundred sixty-oneparticipants (509 eyes) in these 4 groups were included: 53 normal individuals (N; 106 eyes), 112 glaucoma patients (OAG; 212 eyes), 52 glaucoma suspects (GS; 103 eyes), and 44 patients with ocular hypertension (OHT; 88 eyes). The patients who had had an incisional ocular surgery were excluded. All participants underwent IOP evaluation with DCT and GAT and AL, CCT, and CH measurements. The influence of age, sex, AL, CCT, CH, OPA, and glaucoma diagnostic status on Delta IOP was evaluated using correlation analysis and analysis of variance (ANOVA). Right (OD) and left eyes (OS) were analyzed separately. Results: Delta IOP was higher in eyes with longer axial lengths (OD: r = 0.142, P = 0.02; OS: r = 0.233, P < 0.001). Delta IOP also correlated with CH (OD: r = -0. 127, P = 0.04; OS: r = -0.169, P = 0.01), in which the Delta IOP increased as CH decreased (corresponding to less rigid corneas). OPA also correlated negatively with Delta IOP, but the correlation was only statistically significant in left eye (OD: r = -0.112, P = 0.08; OS: r = -0.124, P = 0.05). Age, CCT, sex, and diagnostic status did not influence Delta IOP significantly. Conclusions: GAT underestimated IOP more compared with DCT in patients with longer axial length and in patients with lower corneal hysteresis.