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A comparison of four methods of tonometry: method agreement and interobserver variability
The British Journal of Ophthalmology
|June 21, 2005
Summary
This study compared four intraocular pressure (IOP) measurement devices. The Goldmann applanation tonometer (GAT) showed good agreement, while others had significant differences, limiting their routine clinical use.
Area of Science:
- Ophthalmology
- Biomedical Engineering
- Clinical Measurement
Background:
- Accurate intraocular pressure (IOP) measurement is crucial for diagnosing and managing glaucoma and ocular hypertension.
- Various tonometric methods exist, each with potential variations in accuracy and agreement.
Purpose of the Study:
- To compare the inter-method agreement of intraocular pressure (IOP) measurements obtained from four different tonometric devices.
- To assess the reliability and clinical applicability of the Goldmann applanation tonometer (GAT), Tono-Pen XL, ocular blood flow tonograph (OBF), and Canon TX-10 non-contact tonometer (NCT).
Main Methods:
- A randomized study involving 105 patients with ocular hypertension or glaucoma.
- Intraocular pressure (IOP) was measured using Goldmann applanation tonometer (GAT), Tono-Pen XL, ocular blood flow tonograph (OBF), and Canon TX-10 non-contact tonometer (NCT).
- Bland-Altman analysis was employed to assess interobserver and inter-method agreement for IOP measurements.
Main Results:
- Good interobserver agreement was found for the Goldmann applanation tonometer (GAT) (bias +/-2.6 mm Hg).
- Agreement between GAT and other methods varied: Tono-Pen XL (bias +/-6.7 mm Hg), Ocular Blood Flow tonograph (OBF) (bias +/-5.5 mm Hg), and Non-Contact Tonometer (NCT) (bias +/-4.8 mm Hg).
- The OBF and NCT showed significant underestimation and overestimation of GAT measurements at different IOP levels, with repeatability coefficients ranging from +/-2.2 mm Hg (GAT) to +/-4.3 mm Hg (Tono-Pen XL).
Conclusions:
- The Goldmann applanation tonometer (GAT) demonstrated good interobserver agreement, and the Non-Contact Tonometer (NCT) showed moderate agreement with GAT.
- Significant discrepancies between the Goldmann applanation tonometer (GAT) and both the Ocular Blood Flow tonograph (OBF) and Tono-Pen XL suggest these methods may not be suitable for routine clinical IOP measurement in adult eyes.
- Further research may be needed to refine objective IOP measurement techniques for clinical practice.
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