Comparison of the iCare rebound tonometer and the Goldmann applanation tonometer over a wide IOP range

Abstract

Background: The aim of this study was to compare the intraocular pressure (IOP) results measured by the iCare rebound tonometer with those obtained by the Goldmann applanation tonometer (GAT) over a wide range of IOP values. Furthermore, the comfort level of the iCare measurement was evaluated.

Method: The study included 75 eyes of 75 patients. The patients were divided into three groups (7-15 mmHg n = 25, 16-22 mmHg n = 25, 23-60 mmHg n = 25). The measurements were taken by two independent observers in a masked fashion. All patients were asked about discomfort during the iCare measurement. To establish the agreement between the two devices, a Bland-Altman analysis was performed.

Results: Overall, the 95% confidence interval of the differences between the two devices was -8.67 to 10.25 mmHg and in 62.7%, the iCare measurement was within +/-3 mmHg of the GAT measurements. The distribution of the differences in IOP was similar, from 7-22 mmHg. In the higher IOP range (23-60 mmHg), however, the deviation was almost twice as large. The measurement with the iCare tonometer was well tolerated; 100% of the patients denied any discomfort.

Conclusions: The iCare tonometer is a mobile alternative to GAT in a low to moderate IOP range, but our findings show a greater deviation than previously reported. In high IOP values, measurements with the iCare tonometer do not correlate well with GAT.