Assessment of factors affecting the difference in intraocular pressure measurements between dynamic contour tonometry and goldmann applanation tonometry.

ABSTRACT

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 (ΔIOP=DCTIOP- GATIOP). 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 ΔIOP was evaluated using correlation analysis and analysis of variance (ANOVA). Right (OD) and left eyes (OS) were analyzed separately. RESULTS: ΔIOP was higher in eyes with longer axial lengths (OD r=0.142, P=0.02; OS r=0.233, P<0.001). ΔIOP also correlated with CH (OD r=-0. 127, P=0.04; OS r=-0.169, P=0.01), in which the ΔIOP increased as CH decreased (corresponding to less rigid corneas). OPA also correlated negatively with ΔIOP, 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 ΔIOP significantly. CONCLUSIONS: GAT underestimated IOP more compared with DCT in patients with longer axial length and in patients with lower corneal hysteresis.