[Metrological controls for impression tonometers - ensuring quality standards in ophthalmology]

Area of Science:

• Ophthalmology
• Metrology
• Medical Device Engineering

Background:

• Impression tonometers measure intraocular pressure (IOP) for glaucoma diagnosis and surgical monitoring.
• Mandatory metrological controls in Germany ensure tonometer accuracy and patient safety.
• Specialized test devices developed by Physikalisch-Technische Bundesanstalt (PTB) are used for these controls.

Purpose of the Study:

• To evaluate the suitability and accuracy of existing test devices for impression tonometers.
• To assess the performance of these devices against established metrological standards.
• To ensure the reliability of IOP measurements in clinical and surgical settings.

Main Methods:

• Investigated 18 test devices from various German metrology and testing institutions.
• Assessed measurement accuracy and suitability for metrological control procedures.
• Analyzed parameters including tonometer mass, plunger-lever-pointer system mass, and plunger displacement using statistical methods.

Main Results:

• The majority of investigated test devices are suitable for metrological controls of impression tonometers.
• Most devices performed within permissible error tolerances for IOP measurement.
• The reference tonometer itself showed a deviation in one parameter, which was accurately identified by all test devices.

Conclusions:

• Test devices for impression tonometers are generally reliable when properly maintained.
• Regular recalibration, at least every three years, is essential to maintain device accuracy.
• Even older devices (20+ years) remain fit for purpose with appropriate maintenance and calibration.