Dear Editor,

COVID-19 brought about significant changes in the way ophthalmologists practice and manage their patients. Especially with the appearance of the Omicron variant, fear and risk of transmission have increased, leading to changes in the way practices manage patients. Of the equipment suspended from use, non-contact air jet tonometers have been the most affected due to some evidence that suggested that this technology can lead to aerosolization and dissemination of viral particles [1]. There has been some evidence to suggest that SARS-CoV-2 can be detected in the eyes of COVID-19 patients and therefore potentially lead to transmission [2]. However, there has also been evidence pointing to the contrary, suggesting that risk of transmission through the ocular surface is very low [3]. Nonetheless, to err on the side of caution, most ophthalmology practices have temporarily suspended the use of certain non-contact tonometers in order to ensure patient safety.

Within the category of non-contact tonometers is the Ocular Response Analyzer (ORA; Riechert Ophthalmic Instruments, Inc., Buffalo, NY, USA). It measures intraocular pressure (IOP) and corneal hysteresis utilizing a pulse of pressurized air. Corneal hysteresis has been shown to be a proven clinical tool in the prognosis of glaucoma, through correlation with features of structural or functional progression (Table 1). Just like other non-contact tonometers, a general consensus among ophthalmologists has been adopted to suspend the ORA from clinical use in order to prevent any possible COVID-19 transmission. The current dilemma lies in whether enough evidence exists to limit the use of air jet instruments, and whether or not it is more beneficial for glaucoma patients to have corneal hysteresis measured for their disease.

Table 1 Summary table of the correlation between corneal hysteresis and glaucoma progression
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In our glaucoma practice, the ORA was in use until the onset of the pandemic. We looked for a subset of patients who had hysteresis measurements prior to the pandemic and who continued to follow-up throughout the pandemic. In this group, 44 patients (71 eyes) with primary open-angle glaucoma (POAG) had a mean (± SD) corneal hysteresis of 9.24 ± 1.55. This is significantly less than our control group (40 patients, 75 eyes), which had a mean (± SD) corneal hysteresis of 10.1 ± 1.3 (p < 0.05; data not shown). Over the course of the pandemic, many POAG patients exhibited an increased severity of their glaucoma, determined by structural changes on slit lamp biomicroscopy, with a 19% increase in patients developing severe glaucoma. Additionally, the majority of patients had a worsening progression of their glaucoma and an increase in medications used (1.90 ± 1.13 vs. 2.47 ± 1.09, p < 0.05). Further analysis of this patient cohort was conducted to determine whether or not a lower pre-COVID corneal hysteresis was associated with future medical or surgical interventions. Of the 44 POAG patients, 11 patients (25%) underwent surgical interventions compared to 0 patients in the control group (Table 2). These POAG patients also had low corneal hysteresis (8.6 ± 1.3). When assessing for medical intervention, 55% of POAG patients exhibited increases in medication compared to only 7.5% in the control group.

Table 2 Interventions in control and POAG patients with low corneal hysteresis
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Corneal hysteresis is one of many parameters used for glaucoma risk stratification, but it is the one that was most affected by COVID-19. With every clinical decision, there is a risk–benefit analysis that clinicians conduct aiming for the best patient outcome. With the improved preventative protocols currently in place for COVID-19, and with vaccinations and mask requirements, we believe that the suspension of the air jet technologies like the ORA from clinical use should be reconsidered. By lacking hysteresis measurements, we may be providing a disservice to patients with progressive glaucoma that require more frequent follow-up and interventions.