Tonometer calibration in Brasília, Brazil

To determine calibration errors of Goldmann applanation tonometers in ophthalmic clinics of Brasília, Brazil, and correlate the findings with variables related to tonometers model and utilization.

Tonometers from ophthalmic clinics in Brasília, Brazil, were checked for calibration errors. A standard Goldmann applanation tonometer checking tool was used to asses the calibration error. Only one trained individual made all verifications, with a masked reading of the results. Data on the model, age, daily use, frequency of calibration checking and the nature of the ophthalmic department--private or public--were collected and correlated with the observed errors.

One hundred tonometers were checked for calibration. Forty seven percent (47/100) were out of 1 mmHg range at least at one point checking. Tonometers mounted to slit lamp, with less than 5 years, used in less than 20 patients daily, that had a calibration check on a yearly basis, and those from private office exhibit a lower rate of inaccuracy, but only the first variable was statistically significant. Sixty one percent of tonometers on public hospitals were out of calibration.

Calibration of tonometers in the capital of Brazil is poor; those from general hospitals are worst, and this fact can lead to inaccurate detection and assessment of glaucoma patients, overall in the population under government assistance.