Research demonstrates how tears ejected from the eye during a less frequently used glaucoma screening procedure could potentially spread viruses and other pathogens, including the one that causes COVID-19. The study, published in the journal Physics of Fluids, and led by scientists from the Indian Institute of Science and the Narayana Nethralaya Foundation, warns optometrists to be aware of the potential for contamination and take appropriate precautions.

Non-Contact (Air Puff) Tonometers

Air-puff non-contact tonometers are seldom used by newly trained optometrists and almost never used by ophthalmologists. They rely on a puff of air emitted by the machine to bounce off the eye and indirectly measure its pressure.  The most common risk factor for developing glaucoma is elevated internal eye pressure, also known as intraocular pressure (IOP). Older methods of testing IOP utilize a non-contact tonometer to blow a puff of air at the surface of your eye.  

For the study, the research team took high-speed images of eyes undergoing the tonometer test to see how liquid film of tears on the eye surface responded to the air puff. What they found was that the film expanded and spilled out beyond the eyelid. The images also captured the cornea, the clear outer layer at the front of the eye, retracting away from the oncoming air.

Tracking Tears

“The cornea is like an elastic surface,” explained study author Saptarshi Basu. “So, as it deforms and as it recovers its shape, it gives the eye an additional kick.” A capillary wave, combined with the corneal deflection, expands the tear fluid and disperses it in droplets. 

 After tracking the speed of the fluid as it left each eye, the team estimated that the droplets could travel up to a meter (3.28 feet) away from the patient. This would likely not affect the patient having their eye pressure measured but could jeopardize the examiner.

This distance can vary depending on the airflow in the room. The more moisture in the eye, the more droplets are created, so the study authors recommend avoiding eye drops before the tonometer test unless medically required.

Why This May Be Dangerous

The authors clearly state that their study has many limitations. First, the sample size is small, and any chance of these droplets causing any infection might be limited by the droplets evaporating.  Second, the amount of virus or bacteria in the spray could be insignificant and cause no problems.

 Luckily, ophthalmologists primarily use applanation tonometry, which may use disposable tips or reusable tips after sterilization. 

This study encourages optometrists and ophthalmologists to implement added safety precautions, such as better room ventilation and cleaning procedures, including the disinfection of nearby surfaces and devices following each glaucoma screening, if they are using non-contact air-puff tonometry. Don’t hesitate to ask your doctor whether or not the room was properly disinfected since the last tonometer test was given.

This article was reviewed and edited for accuracy by Alan Robin, M.D., a Responsum Health Advisory Council member, ophthalmologist, glaucoma treatment specialist, and leader in the clinical management and scientific study of the disease.

*American Institute of Physics. (2021, Sep. 14). Noninvasive Eye Procedure Provides Potential Pathway for Virus, Disease Carriers. Science Daily. https://www.sciencedaily.com/releases/2021/09/210914111226.htm