Tell me quick - how clean are my glasses?

Almost every second European wears glasses. Due to their position in the middle of the face, their proximity to the mouth and nose and their frequent contact with the skin and hands, many microorganisms can be found on glasses. A new study at Furtwangen University (HFU) has shown that a tried and tested method from hygiene monitoring is also ideal for assessing how well glasses have been cleaned within seconds.

"We've been researching the microbial contamination of glasses and similar surfaces for many years. Until now, there was no method that could be used outside of a laboratory and by laymen to quickly show how effective a cleaning method for glasses is," explains study head Prof. Dr. Markus Egert, who teaches microbiology and hygiene on the HFU Schwenningen campus. In order to show how dirty a pair of glasses is, the measurement of the adenosine triphosphate (ATP) content of surfaces is now being used.

“ATP is the chemical energy currency of life and is produced by all living cells,” explains Prof. Egert. “The ATP content of a surface has therefore long been used to determine contamination with cells of animal or microbial origin, for example in the food industry.”

For a measurement, the surfaces are rubbed with a swab. The collected ATP then leads to a chemical reaction that results in light emission, which can be measured. The amount of light measured is proportional to the amount of ATP and thus to the contamination of the surface with cellular material. A measurement only takes a few seconds and can be carried out almost anywhere using simple and handy devices.

The study showed for the first time that the ATP content of worn glasses correlates positively with the amount of bacteria that do not require oxygen for their growth. The more of these bacteria on the glasses, the higher the ATP content. These bacteria originate primarily from the skin and hands of people wearing glasses and have already been identified as being very common on glasses in earlier studies by Egert. They also include agents that are potentially hazardous to health.

For the study, six classic spectacle cleaning methods were examined to see how well they reduce the ATP content, i.e. clean the spectacles. All methods showed good results. The best results were achieved with moist wipes without alcohol, which are also particularly gentle on the surfaces of the glasses.

“The ATP method is a simple method that can be used to demonstrate very quickly how well a cleaning method for spectacles works, for example in an optician's store or at an optical trade fair,” summarizes Prof. Egert. Further research is being carried out into the question of the ATP or microbe content at which spectacle surfaces should be classified as a health risk.

The new study was carried out by a team of researchers from Furtwangen University, the University of Tübingen and Carl Zeiss Vision International GmbH, Aalen, and was funded by the Federal Ministry of Education and Research as part of the CoHMed - Connected Health in Medical Mountains project at Furtwangen University. It was published in the journal External link opens in a new window:“BMC Research Notes” mit dem Titel: “Using ATP measurements to rapidly evaluate the cleanliness of spectacle surfaces”.