| Sumario: | Background: Goldmann applanation tonometry is a process of measuring the pressure inside the eye which is essential in many areas of ophthalmology. There are however many sources of error acting upon this process. One potential error is the incorrect calibration of the tonometer. With very little literature available, an audit of tonometer calibration was undertaken to assess the accuracy of calibration as well as the frequency of calibration checks.Method: Calibration checks were made on 24 Goldmann applanation tonometers at the test points of 0, 2 and 60mmHG. A questionnaire concerning the use of calibration checks by hospital staff was also used. Results Sixty seven per cent (n=16) of tonometers were found to have some degree of error at some point in their range (mean 1.5mmHG SDO.72). When an acceptable error of less than 1mmHg is taken into account, 62.5 per cent (n=15) of tonometers showed an error (mean 1.62mmHg SD 0.67). At the most critical test point (10mmHg) 41.7 per cent (n=10) of tonometers had an error greater than or equal to 1mmHg (mean 1.45mmHg SD 0.49).No statistical association existed between calibration errors and any particular test point. There was, however, a statistically significant difference between all test points and a theoretically perfect tonometer which was most evident at the 20mmHg test point (p=0.001). The largest proportion of staff, 43 per cent (n=15), claimed that the last time they made a calibration check was some time in the past year. Nine per cent did not consider themselves proficient at checking the calibration of tonometers. Conclusion: Statistically significant errors were found, and with the varied use of calibration checks from individual operators, the implementation of regular, recorded calibration checks is indicated.
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