Many questions surrounding COVID-19 remain unanswered. We’re certainly encountering significant debates on SARS-CoV-2/COVID-19 experiences, especially as they relate to the likely potential for eye transmission and the actual rate of eye complications and their implications.
Gaps in knowledge remain, but let’s separately review each of these issues and what we know so far. How we prepare now and successfully educate patients on these important questions will help determine how much of an impact a potential second wave might have.
The eye appears to be a vector for viral replication and possible downstream transmission from the ocular surface to the respiratory and gastrointestinal tract areas.1,2 However, little evidence suggests viral transmission occurs through the eye.3 Researchers have documented SARS-CoV-2 receptors in the eye, possibly explaining the viral trophism to the ocular tissue.2
Co-expression and protein interaction network analysis uncovered that the mitochondrial function-related genes in the cornea contribute to the dissection of SARS-CoV-2 susceptibility and potential therapeutic interventions.2
In a series of COVID-19 patients diagnosed via pharyngeal swab and broncho-alveolar lavage, all ocular tissues and fluid were free of RNA detection with quantitative reverse transcription PCR testing.2 The researchers determined that late-stage COVID-19 patients might not harbor an ocular reservoir of SARS2, thereby making it likely that transmitting SARS-CoV-2 via ocular tissues and fluids is low.1 However, it’s possible the viral load in real time PCR testing of human tears may remain below detection threshold levels.2
In addition, when any viral load is detected on the ocular surface, it might come directly from the sinuses.3 The eye’s microbiome, along with natural defense mechanisms (e.g., lactoferrin and IgA and the blink mechanism), may keep the probability of SARS-CoV-2 binding to ACE2 receptors low, thereby protecting the eye from the coronavirus.1,4
Obviously, if clinicians are seeing any patients positive for COVID-19 and are engaged in seeing any at-risk patients, special precautions should include eye protection (tight-fitting goggles), along with a suitable N95 mask since there remains the possibility of viral shedding and potential for transmission through the eye.
Research has reported follicular and hemorrhagic conjunctivitis in patients with COVID-19.5 Conflicting information exists on the actual rate of COVID-related eye complications. Several reports show a low percentage of COVID-19 positive patients with conjunctivitis (probably less than 5%).5
Other reported complications associated with COVID-19 infection include episcleritis, corneal neuropathies, optic neuritis, uveitis, retinitis and exacerbations of dry eye.5,6 Again, whether the ocular surface can serve as a reservoir for transmitting infection remains uncertain and is under debate.3,6
Fortunately, we have learned a great deal about best practices for reducing risk, how to best detect COVID-19 infections and even how we might reduce morbidity/mortality once infection has occurred. But, when following the data collected to date, it’s easy to see that there’s still much we need to learn about this illness.
The debates will continue as we strive to thwart this dreaded disease. We will hopefully have an effective and safe vaccine soon, along with more effective treatment options and directives on how to treat this disease. In the meantime, continue to take every measure to protect your patients, staff and yourself.
We must remain vigilant not only in paying close attention to ocular manifestations related COVID-19 but also sorting out the other questions that remain.
1. Bayyoud T, Iftner A, Iftner T, et al: Absence of severe acute respiratory syndrome-coronavirus-2 RNA in ocular tissues. Am Rep. 2020;19:100805.
2. Guemes-Villahoz N, Burgos-Biasco B, Vidal-Villegas B, et al. Novel insights into the transmission of SARS-CoV-2 through the ocular surface and its detection in tears and conjunctival secretions: a review. Adv Ther. August 18, 2020. [Epub ahead of print].
3. Personal communication, Mark Willcox, PhD.
4. Yuan J, Dan F, Xue Z, et al. Co-expression of mitochondrial genes and ACE2 in cornea involved in COVID-19 infection. bioRxiv. July, 24, 2020. [Epub ahead of print].
5. Cimberle M. Ophthalmologists need to stay vigilant for ocular manifestations of COVID-19. Healio. www.healio.com/news/ophthalmology/20200812/ophthalmologists-need-to-stay-vigilant-for-ocular-manifestations-of-covid19. August 18, 2020. Accessed October 5, 2020.
6. Jones L, Walsh K, Wilcox M, et al. The COVID-19 pandemic: important considerations for contact lens practitioners. Cont Lens Anterior Eye. 2020;43(3):196-203.