Reutilization of disposable rebound tonometer probes: Risk or return?

An advantage of rebound tonometry (RT) is its ease of use so that it can also be operated by health care technicians. However, the cost of the disposable measuring probes is high and their reuse carries the risk of infection. Therefore, this study aims to objectify the potential risk of bacterial transmission by RT.

Our experimental setting consisted of two experiments. The first aimed to quantify the number of bacteria on a tonometer probe after immersion in a bacterial suspension in vitro. The experiment was carried out with two different bacteria and compared with results from a Goldmann tonometer probe. The second experiment tested whether bacteria could be transmitted by simulating reuse of a nondisinfected rebound tonometer probe.

First experiment: After immersion of the rebound tonometer probe, we measured a bacterial count of 2.43 × 10⁶ Escherichia coli (EC) and 1.12 × 10⁶ Pseudomonas fluorescens. In total, 1.09 × 10⁷ bacteria for EC and 2.61 × 10⁶ for Pseudomonas fluorescens (PF) were measured on the Goldmann tonometer probe. Second experiment: A bacterial transmission could be detected in 36% of cases in which reuse of nondisinfected tonometer probes was simulated.

These results show that despite the small surface of the rebound tonometer probe, there is a clear risk of bacterial transmission. Thorough disinfection according to general standards should be mandatory if the tonometer probes are to be reused.