Purpose: To establish the repeatability of ocular blood flow (OBF) pneumotonometry and its agreement with Goldmann tonometry.
Design: Instrument evaluation study.
Participants: Ten female healthcare professionals.
Methods: Intraocular pressure (IOP) was measured by one experienced ophthalmologist in both eyes of 10 healthy female subjects on 10 different occasions at the same time of day. The two methods were performed by alternate allocation, and laterality was chosen by random order. Repeatability coefficients and agreement plots were calculated by using the Bland-Altman method.
Main outcome measures: Intraocular pressure repeatability coefficients.
Results: Mean IOPs were 15.6 mmHg (right) and 15.1 mmHg (left) by OBF pneumotonometry and 12.6 mmHg (right) and 12.4 mmHg (left) by Goldmann tonometry (P < 0.001). The repeatability coefficients were 7.06 (right) and 7.66 (left) for the OBF pneumotonometer and 4.81 (right) and 3.87 (left) for the Goldmann tonometer. With regard to agreement, the OBF pneumotonometer read significantly higher than did the Goldmann tonometer. The mean bias for the right eye was 2.92 (95% limits of agreement, -4.37 to 10.20), and for the left eye it was 2.68 (95% limits of agreement, -3.93 to 9.28).
Conclusions: In our group of healthy females, the repeatability of the OBF pneumotonometer was worse than that of the Goldmann tonometer. This casts doubt on the value of the OBF pneumotonometer as a tool for measuring IOP. The agreement plots indicate that the OBF pneumotonometer may produce significant numbers of false-positive results in screening programs.