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Even-number Measurement Bias With Goldmann Applanation Tonometry
Anne Rozwat1, Daniel K Roberts1,2,3
1Department of Clinical Education, Illinois Eye Institute, Illinois College of Optometry.
Journal of Glaucoma
|November 26, 2019
Summary
Examiners show a tendency to record Goldmann applanation tonometry (GAT) intraocular pressure (IOP) readings as even numbers. This even-number preference in IOP measurements varies with the IOP level, being less apparent in the 21-24 mmHg range.
Area of Science:
- Ophthalmology
- Biostatistics
- Clinical Measurement
Background:
- Goldmann applanation tonometry (GAT) is a standard method for measuring intraocular pressure (IOP).
- Previous observations suggested a potential bias in GAT readings favoring even numbers.
- Limited research has explored the extent and variability of this phenomenon.
Purpose of the Study:
- To investigate the distribution of GAT-measured IOP values in a large dataset.
- To determine if a preference for even-numbered IOP readings exists.
- To analyze how this potential bias varies across different IOP levels.
Main Methods:
- Analysis of a large dataset comprising 69,537 right eye GAT IOP measurements.
- Statistical examination of the distribution of recorded IOP values.
- Assessment of the even-number preference in relation to specific IOP ranges.
Main Results:
- A significant tendency for even-numbered IOP values was observed.
- This even-number preference was minimal between 21-24 mmHg.
- The bias towards even numbers increased as IOP readings moved further from the 21-24 mmHg range.
Conclusions:
- Data suggest an examiner proclivity to record GAT readings as even numbers.
- This examiner bias in IOP measurement is not uniform and varies with the IOP level.
- Further investigation into measurement and recording practices in tonometry is warranted.
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