Abstract
Purpose: :
To compare the accuracy of intraocular pressure (IOP) measurement by the ICare rebound tonometer (ICT) with that by the Goldmann Applanation Tonometer (GAT) and the pneumatonometer (PT) across a range of central corneal thicknesses (CCTs) and ages.
Methods: :
One observer obtained IOP measurements in 125 eyes of 63 participants using the ICT. A GAT reading was obtained by an experienced technician, before or after the ICT measurement. IOP measurements were also obtained using the PT. The order of IOP measurements by each of the devices was randomized, and the observers obtaining the measurements were masked to the values obtained by the other devices. CCT was measured in all eyes with ultrasound pachymetry. Patients with or without glaucoma and with normal and abnormal corneas were included.
Results: :
The mean IOP obtained by GAT was 14.85 mmHg (SD 6.58, range 5-46), by ICT was 13.82 mmHg (SD 6.05, range 5-42), and by PT was 18.19 mmHg (SD 5.82, range 9-46.5). The mean difference between measurements obtained by the ICT and the GAT (ICT-GAT) was -1.07 mmHg (SD 4.44). The mean difference between measurements obtained by the ICT and the PT (ICT-PT) was -4.40 mmHg (SD 3.69). The mean difference between measurements obtained by the PT and the GAT (PT-GAT) was 3.26 mmHg (SD 3.68). The mean difference between measurements obtained with the ICT and the GAT was significantly less than that between those obtained with the PT and the ICT (p<0.001) and between those obtained with the PT and the GAT (p<0.001). Bland-Altman plots with linear regression showed good agreement between the ICT and the GAT across the range of measured IOPs. The PT gave consistently higher IOP measurements across the range of measured IOPs compared to the GAT (p<0.001) and the ICT (p<0.001). The mean CCT was 555 microns (SD 63.7, range 410-936). There was no significant correlation between CCT and ICT IOP measurements (p=0.34), or between CCT and the difference between IOP measurements obtained with the ICT and the GAT (p=0.47). The mean age was 70.16 (SD 12.7, range 30-94). Linear regression analysis revealed that the ICT significantly overestimated the GAT-measured IOP at younger ages, and underestimated it at older ages (p<0.001).
Conclusions: :
There is good agreement between IOP measurements obtained by the ICT and those obtained by the GAT across the measured range of IOPs and CCTs. However, the ICT overestimates the GAT-measured IOP at younger ages, and underestimates it at older ages. The PT consistently produces higher IOP measurements than the ICT or the GAT across the range of measured IOPs.
Keywords: intraocular pressure