The accuracy of clinical applanation tonometry.

The differences between two careful applanation tonometries performed by one and by two observers, respectively, were compared. Two measurements by one observer differed by 2 mmHg or more in 8% of the pairs of measurements and by 3 mmHg or more in 2% of the pairs. One tonometry each by two observers differed by 2 mmHg or more 40% of the pairs of measurement and by 3 mmHg or more in 17% of the pairs. There was no dependence on the intraocular pressure. Possible reasons for the increase in variance are discussed.