First systematic review of COVID-19 colonisation of ocular tissues and secretions
Reviewed by Hadi Ziaei

The authors present the first systematic review summarising all the data regarding SARS-CoV-2 colonisation of ocular and periocular tissues and secretions. They reviewed all publications between December 2019 to April 2020 in the Cochrane Library, Medline, World of Science and Chinese Clinical Trial Register. Of 2422 articles, 11 met the inclusion criteria which included three articles, one review, four letters, two editorials and one correspondence letter. A total of 252 infected patients who underwent conjunctival swabs were identified globally. The prevalence of conjunctivitis was found to be as high as 32% in one study and as low as 0% in another. Altogether, three patients had conjunctivitis with a positive tear-polymerase chain reaction (PCR), eight patients had positive tear-PCR in the absence of conjunctivitis, and 14 had conjunctivitis with negative tear-PCR. This inconsistency may be multifactorial, including low viral load in conjunctival secretions and inappropriate sample collection or handling. The authors acknowledge the paucity of available high-quality information on the subject. It has been shown that the viral cell entry depends on SARS-CoV-2 S protein/ACE2 receptor interaction, and key proteins of the renin-angiotensin-aldosterone system have widely been described in many ocular structures. One in-vitro study demonstrated ACE2 expression and effective binding of the SARS-CoV S240 protein with these receptors on both corneal and conjunctival cells. Given the wide variation in these results, the majority of the data regarding CoV-2 infection of ocular tissues and secretions has to be considered controversial. Nevertheless, infection of these tissues with the SARS-CoV-2 virus cannot be excluded.

Coronavirus disease 2019 (SARS-CoV-2) and colonization of ocular tissues and secretions: a systematic review.
Aiello F, Afflitto GG, Mancino R, et al.
EYE
2020;34:1206-11.