A comparison of clinical performance between disposable and Goldmann tonometers

Applanation tonometry as performed in routine clinical practice is a significant potential vehicle for cross-infection particularly in an emergency eye care setting. The aim of this study is to evaluate the accuracy and reliability of three single-use devices (Tonoshield, Tonosafe, Tonojet) as an alternative to standard Goldmann prisms in an emergency eye department.

All patients attending the eye casualty at the Manchester Royal Eye Hospital for a period of 4 months who required intraocular pressure measurement were eligible for this prospective study. Exclusion criteria were: age below 18 years, corneal anomalies that might affect measurement, and refusal to participate. After taking informed consent, the patient was examined by one experienced nurse practitioner, who measured the intraocular pressure three times. In the first part of the study, we compared the standard Goldmann prism vsTonoshield and Tonosafe prisms, while for the second part of the study we used standard Goldmann, Tonosafe, and Tonojet prisms. Agreement and repeatability tests were carried out on separate samples.

Tonosafe and Tonojet correlated well with standard Goldmann tonometry (P<0.001), while the measurements obtained with Tonoshield were higher, especially for raised intraocular pressure measurements. Tonojet and Tonosafe measurements were more reproducible than Tonoshield measurements.

This study shows that Tonosafe and Tonojet are accurate and reliable alternatives to standard Goldmann tonometry.