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[Sources of error in Goldmann applanation tonometry]
1Klinik für Augenheilkunde, Universitätsklinikum Schleswig-Holstein-Campus Kiel, Arnold-Heller-Strasse 3, Kiel, Germany. fruefer@auge.uni-kiel.de
Summary
Accurate intraocular pressure (IOP) measurement is crucial for glaucoma management. Various factors, including user error and physiological changes, can affect applanation tonometry results, necessitating regular tonometer calibration.
Area of Science:
- Ophthalmology
- Biomedical Engineering
- Optometry
Context:
- Glaucoma management relies on precise intraocular pressure (IOP) monitoring.
- Applanation tonometry is a common method for measuring IOP.
- Potential errors can compromise the accuracy of IOP measurements.
Purpose:
- To identify factors influencing the accuracy of applanation tonometry.
- To detail conditions leading to IOP overestimation and underestimation.
- To provide recommendations for ensuring reliable IOP measurements.
Summary:
- Overestimation of IOP can result from incorrect slit lamp use, external forces, lid contact, blepharospasm, lid retraction, or Valsalva maneuver.
- Underestimation may occur due to insufficient fluorescein staining, poor illumination, corneal edema, post-LASIK changes, accommodation, rapid repeat measures, or hypotension.
- Inconsistent tonometer calibration, abnormal corneal thickness, or astigmatism can cause bidirectional IOP discrepancies.
Impact:
- Highlights the importance of meticulous technique and awareness of confounding factors in IOP measurement.
- Emphasizes the need for regular tonometer calibration (1-2 times annually) to maintain measurement accuracy.
- Aids clinicians in interpreting IOP readings and optimizing glaucoma patient care.
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