Rectifying calibration error of Goldmann applanation tonometer is easy!

Area of Science:

• Ophthalmology
• Ophthalmic instrumentation

Background:

• Goldmann applanation tonometer (GAT) is the gold standard for intraocular pressure measurement.
• Calibration errors in GAT are frequent and often go undetected, impacting clinical accuracy.
• Limitations exist in manufacturer-based repair services for GAT calibration issues.

Purpose of the Study:

• To present a self-taught method for correcting Goldmann applanation tonometer calibration errors.
• To assess the efficacy of an in-house calibration rectification technique for GAT.

Main Methods:

• A pilot study involved 29 Haag-Streit Goldmann tonometers (Model AT 900 C/M).
• The technique included cleaning, lubrication, and, if necessary, counter-weight alignment.
• Calibration error tolerance followed the South East Asia Glaucoma Interest Group criteria.

Main Results:

• 41.3% (12/29) of GATs exhibited calibration errors.
• Cleaning and lubrication resolved errors in 91.6% (11/12) of faulty instruments.
• Only one tonometer required counter-weight adjustment.

Conclusions:

• In-house calibration error rectification for GAT is feasible.
• Basic cleaning and lubrication, performable by eye care professionals, resolve most GAT calibration issues.
• This approach can significantly decrease GAT instrument downtime.