NCT Safer in Practice Than Report Alleges
A news story published online September 28 and in the October print issue (“Avoid Tonometry With High Tear Volume”) provided an overview of a Journal of Glaucoma publication, along with editorial comments.1 Unfortunately, the reporting largely misrepresented the conclusions, and the essence, of the study (“Quantitative high-speed assessment of droplet and aerosol from an eye after impact with an air-puff amid COVID-19 scenario,” by Shetty et al.). The news story proclaims, “Even non-contact options can create droplets and aerosols, increasing the risk of contamination.” The article goes on to state: “Researchers are now recommending clinicians avoid non-contact tonometry (NCT) in patients with high tear volume, whether natural or due to eye drops, as the diagnostic procedure could spread droplets to the device and the operator.”
By focusing on these unlikely outcomes, the news story leads readers to believe that non-contact tonometry is unsafe and, in doing so, fails to accurately portray the overall findings of the study by Shetty, which were positive with regards to the safety of non-contact tonometry. The study demonstrated that droplet spray did not occur when the instrument was used “in the natural setting.” Droplets were only detected when supplemental artificial tears were experimentally added to the eye—and it took two drops to produce substantial scatter. However, this is not how non-contact tonometers are intended to be used and not how they are used routinely in clinic. NCTs are used without drops of any kind.
Beyond this, I implore authors of medical and scientific articles to use the term “aerosols” properly as to not misinform readers. Even the Shetty paper used this term haphazardly. An aerosol is a tiny particle suspended in air. Particles of 100µm and larger are not usually considered aerosols. In the context of the COVID discussion, when talking about aerosols we are generally talking about 10µm or less. The Shetty study depicted “droplets” ranging from 100µm to 500µm. Droplets this large will not become airborne. There is no credible published evidence that NCTs generate “aerosols.” Finally, it is important for readers to be made aware that the probability of SARS-CoV-2 being present in tears is exceedingly low based on published evidence.2-4
All things considered, with respect to tonometry and COVID, non-contact tonometers are likely the safest option. Goldmann requires direct eye contact, close patient-clinician distance and, frequently, lid-holding. Handheld tonometers also require relatively close distance, direct contact and frequent lid-holding. NCTs provide the maximum possible distance between patient and clinician, no lid-holding and no mucous membrane contact.
This briefing did not present a balanced view of the Shetty paper, focusing instead on unlikely hypothetical fears. This is a disservice to clinicians and the patients who benefit from these measurements and is unnecessarily damaging to NCT manufacturers’ reputations.
—David A. Taylor, Director
Product Management & Business Development
1. Shetty R, Balakrishnan N, Shroff S, et al. Quantitative high-speed assessment of droplet and aerosol from an eye after impact with an air-puff amid COVID-19 scenario. J Glaucoma. September 17, 2020. [Epub ahead of print].
2. Jianhua Xia MM, Jianping Tong MD, Mengyun Liu MM, et al. Evaluation of coronavirus in tears and conjunctival secretions of patients with SARS CoV 2 infection. J Med Virol. 2020;92(6):589-94.
3. Guan WJ, Ni Z, Hu Y, et al. Clinical characteristics of coronavirus disease 2019 in China. N Engl J Med. 2020:382:1708-20.
4. Yu Jun IS, Anderson DE, Zheng Kang AE, et al. Assessing viral shedding and infectivity of tears in coronavirus disease 2019 (COVID-19) patients. Ophthalmology. 2020;127(7):977-79.
Keep Referrals Within Optometry When Possible
I enjoyed Dr. Fanelli’s article in the June issue entitled “The Dangers of DNR” and just wanted to congratulate him on the creativity and wisdom of his timely commentary. I agree with him that the time has come for our profession to cease the pathological modus operandi of referring non-surgical cases to a surgeon.
There is now a critical mass of highly competent clinical optometrists ready, willing and able to handle medical eye conditions and we, as a profession, need to be doing intra-professional consultations rather than reflexively dumping these patients on eye surgeons. Such a sea change will require a two-step process. First, medically oriented optometrists should seek out their local non–medically inclined colleagues and let them know they would be happy to consult with them. Second, the non–medically inclined optometrists should seek out the more medical colleagues in their area and begin to use them as a resource. The consultant OD should make every good-faith attempt to send the referred patient back to the primary OD. That being said, once any patient leaves your practice to see any OD or MD, there is always the risk of losing such patients (and their family and friends), which is why I would like to see all ODs embrace greater patient care responsibilities.
Again, Dr. Fanelli, thank you for your always excellent articles, but this one was especially timely for our profession. Thank you for your many contributions to enhance the profession of optometry.
—Randall Thomas, OD, MPH