Abstract
Purpose: :
To compare the intraocular pressure (IOP) measurements obtained by a rebound tonometer designed for self-tonometry (RT), the Goldmann applanation tonometer (GAT), and the Pascal dynamic contour tonometer (DCT) in glaucoma patients. Moreover, we investigated the influence of central corneal thickness (CCT).
Methods: :
74 glaucomatous eyes were included in this prospective clinical trial. Rebound tonometry was conducted by the patients themselves, GAT and DCT were performed by three equally skilled observers. The medians and standard deviation for all tonometers were compared. Agreement between the different devices was tested using Bland-Altman plots. Linear regression of the difference between RT and GAT measurements versus the estimated CCT showed, if the CCT led to over- or underestimation of the IOP by using the RT.
Results: :
The mean IOP was 18.09 ± 6.5 mmHg with the RT, 17.38 ± 6.0 with the GAT, and 18.55 ± 4.7 mmHg. The correlation was excellent between RT and GAT (r = 0.896, p < 0.001) and RT and DCT (r = 0.845, p < 0.001). The Bland-Altman scatterplot obtained good agreement between the instruments: mean difference between RT and GAT measurement was 0.45 ± 2.90 mmHg, whereas mean difference between RT and DCT was -0.45 ± 3.59 mmHg. The difference between RT and GAT significantly rose with increasing CCT (p = 0.01) with a 10 % increase in CCT resulting in an 1.9 % increase in the difference. Linear regression analysis disclosed that RT overestimated GAT at higher CCT and underestimated the IOP readings at lower CCT (X-intercept = 514.3 µm).
Conclusions: :
Measurements obtained with the rebound tonometer for self-tonometry showed excellent correlation with the results of applanation and dynamic contour tonometry. RT tends to overestimate the IOP compared to GAT and to underestimate the IOP compared to DCT. RT, GAT and CCT readings indicated the dependency of rebound tonometry on CCT.
Clinical Trial: :
www.germanctr.de, DRKS00000478
Keywords: clinical (human) or epidemiologic studies: systems/equipment/techniques • intraocular pressure