Assessment of the accuracy and reliability of the Topcon CT80 non‐contact tonometer

Abstract

Background:  The reliability of non‐contact tonometers has been reported extensively in the literature. This study was designed to assess reliability of the new Topcon CT80 non‐contact tonometer in normotensive subjects, using the Goldmann tonometer as the standard.

Methods:  The accuracy of the Topcon CT 80 non‐contact tonometer was assessed by comparing its IOP assessments with those of the Goldmann applanation tonometer, on 60 right eyes of young healthy subjects with normal intraocular pressures. Each subject’s intraocular pressure was assessed with each technique on two separate occasions, one week apart. The reliability of each technique was determined by the assessment of its inter‐session repeatability using the Bland‐Altman method. The 95 per cent limits of agreement for the two methods were also determined.

Results:  No statistically significant difference was found between the average intraocular pressures measured with the two techniques (p > 0.05). The inter‐session repeatability indices for the two techniques did not differ significantly (p > 0.05). The mean difference in intraocular measurements between the two techniques was 0.2 ± 1.5-mmHg (mean ± SD) and the 95 per cent limits of agreement were ‐3.14 and +2.74-mmHg, with the non‐contact tonometer returning higher readings than the Goldmann tonometer.

Conclusion:  In this sample of normotensive subjects, the Topcon CT80 non‐contact tonometer proved to be accurate and as reliable as the Goldmann tonometer in the assessment of intraocular pressure. Thus, it can be used as an objective clinical method for the assessment of normal intraocular pressure.

Key words:

• Goldmann tonometry
• limits of agreement
• non‐contact tonometry
• repeatability
• Topcon CT80

ACKNOWLEDGEMENTS

The author acknowledges the kind assistance of Dr Turki AlMubrad in gathering the data for this study and for suggestions on data analysis.