Comparison of the Challenger digital applanation tonometer and the Goldmann applanation tonometer

We compared the Challenger electronic tonometer to the Goldmann applanation tonometer in 70 eyes without corneal abnormalities. There was a good overall correlation between the two machines. Correlations between interobserver readings were excellent, demonstrating that obtaining reproducible measurements is possible with either machine. However, the scattergrams indicated that the Challenger tonometer gave consistently lower readings and showed more variability than the Goldmann tonometer. Additionally, the mean underestimation of intraocular pressure increased as the intraocular pressure increased above 20 mm Hg. Therefore, the Challenger electronic tonometer as presently calibrated is not accurate enough for clinical use in the detection and management of glaucoma.