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Peter Campbell, David Edgar, Rakhee Shah; Agreement of three tonometers with Goldmann Applanation Tonometry (GAT). Invest. Ophthalmol. Vis. Sci. 2019;60(9):2421.
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© ARVO (1962-2015); The Authors (2016-present)
To assess the agreement of three tonometers commonly used by UK community optometrists with GAT.
Participants, 18 years and over, were recruited from a university eye clinic, staff and students. IOP was first measured on the randomly selected study eye using three methods: CT-1P Non-Contact Tonometer (NCT) (Topcon, Topcon Corporation, Tokyo, Japan), Pulsair IntelliPuff (Keeler Ltd., Windsor, UK) and Icare rebound tonometer (Icare®, Helsinki, Finland) by an experienced optometrist (RO1). GAT readings were then obtained in a masked manner by RO1. The force on the probe was initially set at a randomly selected value between 1g and 2g by a second optometrist (RO2); RO1, unable to see the dial reading, adjusted the probe until the end point, and RO2 recorded the measurement. Agreement between NCT, Pulsair, Icare and GAT was assessed using Bland–Altman analysis, and mean differences and 95% limits of agreement (LoA) of measurements calculated. Percentages of IOP readings within ±2mmHg of the GAT reading were calculated.
Forty-one participants were measured by all four tonometers: median age 36 years (IQR: 20,49), 71% female. Results for the study eye (22 right eyes) for each tonometer and agreement compared to GAT are shown in Table 1. Figure 1 displays the Bland-Altman plots for the three tonometers compared to GAT.
The CT-1P NCT had closest agreement to GAT; both Pulsair and Icare recorded mean IOP lower than GAT, and this was significant for Pulsair (p=0.01). 54-56% of measurements were within ±2mmHg of the GAT reading, similar to findings for other non-GAT tonometers. The 95% LoAs for all three tonometers were wide, particularly for Pulsair and Icare. Community optometry eye examinations are the primary source of case finding for glaucoma and ocular hypertension in the UK. Our study suggests that optometrists using Pulsair or Icare to measure IOP could be systematically under-reading IOP. Further work should investigate the clinical impact of these findings on detection of patients at risk of glaucoma.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
Figure 1 Bland Altman plots for each tonomer
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