Jack S. Parker, MD, PhD

In Albert Camus’ “The Plague,” our narrator notes how “… the perplexity of the early days gradually gave place to panic.” And while we fervently hope that our own story of quarantine will differ entirely from Camus’, we do share the same starting point: perplexity. The world has been blindsided by the highly improbable, extreme impact event — N.N. Taleb’s “Black Swan” — one in which radical uncertainty predominates and in which we enter a true emergency period where we must learn, and learn quickly, in the face of the new observed reality.

Jun and colleagues have made a high-profile attempt to gather some of this necessary knowledge in their forthcoming publication, “Assessing viral shedding and infectivity of tears in coronavirus disease 2019 (COVID-19) patients.” From samples of tears obtained from 17 infected patients (none of whom displayed any overt ocular involvement), they conclude there is little evidence that COVID-19 is transmissible by tears alone in patients without active conjunctivitis.

If these findings are correct, it would suggest that “eye rubbers” are not more likely disease transmitters, and that Goldmann applanation is not particularly high-risk.

However, these results should be interpreted with caution. The absence of evidence does not equate to evidence of absence, and it certainly remains theoretically plausible that COVID-19 could be transmitted though the tear-film, this 3-week study of 17 patients notwithstanding.

A true test of these results would be inoculating noninfected individuals with tears collected from the infected. I cannot imagine there would be any volunteers for such a study.

There is a danger in thinking that we know more than we do, and a general precautionary principle may be best applied. In the meantime, we should be researchers, not philosophers, and empiricists, not theorists. And, above all, we should be alert to the cardinal logical fallacy that generates black swans in the first place; that “all you see is all there is.”