Comparison of dynamic contour tonometry, Goldmann and pneumotonometer in ocular hypertension patients and their relationship to pachymetry and ocular pulse amplitude

Abstract

PurposeTo determine the relationship between dynamic contour tonometry (DCT), Goldmann applanation tonometry (GAT) and pneumotonometry (PNT) in ocular hypertension patients (OHT) and their relationship to central corneal thickness (CCT) and ocular pulse amplitude (OPA). MethodsSixty patients (101 eyes) with intraocular pressure (IOP) ≥21mmHg using GAT and normal appearing optic nerve heads and normal visual fields were included. The following tests were performed simultaneously during a single visit: IOP using DCT, GAT and PNT, OPA using DCT and CCT using ultrasound pachymetry. We studied the difference IOP between these 3 tonometers using Wilcoxon non-parametric test and the effect of CCT on IOP and OPA, as well as the relationship between OPA and IOP using Spearman correlation coefficient. ResultsThe median PNT IOP was 24mmHg (inter-quartile range [IQR]: 22–26), median GAT IOP was 22mmHg (IQR: 22–24), and median DCT IOP was 28.2mmHg (IQR: 24.1–30.7). PNT and DCT had higher IOP values than GAT (median 2mmHg and 6.2mmHg, respectively). Mean CCT was 594.5μm (SD 30.0). GAT IOP and DCT IOP showed an increase with increased corneal thickness (r: 0.209; P=0.036 and r: 0.195; P=0.051, respectively). PNT IOP did not change with CCT (r: 0.15; P=0.12). The median OPA was 4.8mmHg (IQR: 3.6–6.1), and significantly increased with GAT IOP (r: 0.38; P<0.001) and with CCT (r: 0.287; P=0.004). This association was unclear with IOP PNT and IOP DCT (r: 0.067; P=0.50 and r: 0.17, P=0.08, respectively). ConclusionsDCT and PNT IOP values were higher than GAT IOP measurements in ocular hypertension patients. GAT IOP showed a significant increase with increased corneal thickness. Increased OPA seems to correlate with increased CCT and IOP, particularly if GAT is used.