Questions and Answers: Non-Contact Tonometer Safety in the COVID-19 Era
Almost 50 years since inventing the Non-Contact Tonometer, Reichert® continues to innovate and pioneer patented non-contact technologies like Corneal Compensated IOP (IOPcc), a better pressure measurement, and Corneal Hysteresis (CH), a measurement consistently shown to be a more powerful predictor of, and strongly associated with, glaucoma progression, more so than key risk factors such as IOP and CCT.A-C
Now more than ever, eye care professionals are concerned about safety, not just for their patients but also for their staff. There has been much debate on the safest way to perform routine eye exams, especially when it comes to tonometry. Reichert is here to answer your questions on the safe use of Non-Contact Tonometers, and provide up-to-date information on best practices to follow.
According to the current research, there is no material evidence that Non-Contact Tonometry is an aerosol generating procedure, and the current science shows the risk of spreading COVID-19 through tears is low and seems to be confined to patients who present with ocular symptoms.
What level of cleaning is required for a Reichert Non-Contact Tonometer?
All Reichert Non-Contact Tonometers are classified as non-critical devices because they contact intact skin, they do not contact the mucous membrane. As such, Non-Contact Tonometers require low-level disinfection.
Note: Goldmann tonometers and prisms are classified as semi-critical and require high level disinfection.
What is the proper cleaning and low-level disinfection procedure for a Non-Contact Tonometer?
Is there a risk of air tube contamination that can spread infections to other patients?
There is no evidence to suggest that contamination can enter the Non-Contact Tonometers air tube and cause harm to other patients.1
Is Non-Contact Tonometry an aerosol generating procedure (AGP)?
There is no material evidence that Non-Contact Tonometry is an aerosol generating procedure. The only publication on this subject is from 1991 by Britt et al. The authors used fluorescence photography to capture visible tear film splatter from the air puff in eyes with the application of supplemental topical fluorescein or artificial tears.1 However, this photographic method is not capable of capturing “aerosolization” as aerosols are particles that are not visible to the eye. Today, it is agreed that the authors used incorrect terminology in describing their findings as “micro-aerosolization”. It should also be noted that the air pulse technology utilized in the study applied 4 to 6 times more force than modern Non-Contact Tonometers, making the tear film splatter much more substantial.2
Is the SARS-CoV-2 virus present in tears?
The primary path of infection is through droplets produced by and entering into the mouth, nose, and lungs.3 Numerous studies evaluated the presence of SARS-CoV-2 in tears and found the risk to be low (0-5.2%) and only present in patients with ocular manifestations such as chemosis, conjunctival hyperemia, or conjunctivitis.4-6
What are the risks of spreading the virus through the eye?
It has been suggested that the eyes might be a portal of entry for the virus because of the presence of ACE receptors, but there is currently no clinical evidence for this theory (and the dermis also contains ACE receptors).7 In addition, there is no evidence that viral particles can be implanted into the eye during Non-Contact Tonometry. The air pulse generating mechanism in Reichert Non-Contact Tonometers is almost completely shielded by the plastic housing of the instrument, making it unlikely for respiratory droplets from patients or clinicians to enter the device.
Is there any evidence of infection spread by use of a Non-Contact Tonometer?
No, the Non-Contact Tonometer has a 50-year record of safety. There are no documented instances of infection being spread by use of a Non-Contact Tonometer.
Does Non-Contact Tonometry provide a safer working distance between clinician and patient, compared to other forms of tonometry?
Yes, the typical clinician-patient distance is approximately 3 feet and rarely requires the clinician to touch the eyelid.
Sources of Questions and Confusion
Doctors should follow instrument IFUs (Instructions For Use) but:
• CDC, FDA, Joint Commission, and professional organizations (AAO) may not always be in agreement and often publish conflicting recommendations
• Regardless of what the authorities say, doctors don’t keep up with changes, often do what is most efficient in their practices or what they think is right
• There are regional differences in requirements
• Government, Hospitals, and Institutions are more likely to insist on updated cleaning & disinfection instructions from the manufacturer. This requires testing and validation of new methodologies (time and $)
CDC Categorization and Definitions
Infection Control Basics and Important CDC Terms
Tonometers that touch the cornea with a reusable tip are considered to be semi-critical devices.
The exterior of all tonometers (bodies, screens, headrests, etc), especially handheld models, should be wiped down after each patient use.
• Manufacturer instructions will vary by instrument
• In general 70% isopropyl alcohol or 5000 ppm bleach wipes are considered to be safe and effective.
Reichert Products and Disinfection Level
- Reichert has high-level disinfection products that must be disinfected between patient use:
- • CT210 and CATS Prism
- • Model 30 Pnuematonometer
- • iPac Pachymeter
- All other Reichert products, and portions of the above products that do not directly touch the cornea, must be low-level disinfected or cleaned in the areas outlined below:
- • Forehead rests & Chin rests
- • Handles / bodies of Tono-Pen, iPac, PT100, PSL, etc
- • Screens, plastic housings, metal housings, etc
- Historically we recommended soapy water for housings and isopropyl alcohol for head rests/ chin rests
- • We are testing common disinfectants such as bleach, alcohol, and other solvents and will provide updated cleaning instructions in the coming months
COVID-19 and Tonometry... What do we know so far?
• Widespread concern regarding the presence of the virus in tears and the ability of the virus to enter through the eye.
• The primary path of infection is through droplets produced by and entering into the mouth, nose, and lungs.1
• Numerous studies evaluated the presence of SARS-CoV-2 in tears and found the risk to be low (0-5.2%) and only present in patients with ocular manifestations such as chemosis, conjunctival hyperemia, or conjunctivitis.2-4
• Evidence that eyes may be a portal of entry for the virus is speculative.5
• The current science shows the risk of spreading COVID-19 through tears is
low and seems to be confined to patients who present with ocular symptoms
Non-Contact Tonometer (Reichert 7CR)
• Automated, technician friendly
• Non-contact: Eliminates the need for high-level disinfection
• Accuracy generally considered to be acceptable
• Some models offer superior accuracy and additional diagnostic information - ie: ORA G3 / 7CR, corneal hysteresis
• Use of these devices can help reduce dependency on GAT
Advantages: No cumbersome disinfection required.
• Offers furthest clinician-patient distance.
• Lid-holding or patient contact seldom required.
• No costly disposables.
• Superior accuracy with ORA G3 & 7CR.
Disadvantages: Expensive initial cost vs other tonometers
• Patient and doctor NCT “stigma” stemming from older devices
Tonometers by Type, Use, and Disinfection Method