The eye as the discrete but defensible portal of coronavirus infection

Oculo-centric factors may provide a key to understanding invasion success by SARS-CoV-2, a highly contagious, potentially lethal, virus with ocular tropism. Respiratory infection transmission via the eye and lacrimal-nasal pathway elucidated during the 1918 influenza pandemic, remains to be explored in this crisis. The eye and its adnexae represent a large surface area directly exposed to airborne viral particles and hand contact. The virus may bind to corneal and conjunctival angiotensin converting enzyme 2 (ACE2) receptors and potentially to the lipophilic periocular skin and superficial tear film with downstream carriage into the nasopharynx and subsequent access to the lungs and gut. Adenoviruses and influenza viruses share this ocular tropism and despite differing ocular and systemic manifestations and disease patterns, common lessons, particularly in management, emerge. Slit lamp usage places ophthalmologists at particular risk of exposure to high viral loads (and poor prognosis) and as for adenoviral epidemics, this may be a setting for disease transmission. Local, rather than systemic treatments blocking virus binding in this pathway (advocated for adenovirus) are worth considering. This pathway is accessible with eye drops or aerosols containing drugs which appear efficacious via systemic administration. A combination such as hydroxychloroquine, azithromycin and zinc, all of which have previously been used topically in the eye and which work at least in part by blocking ACE2 receptors, may offer a safe, cost-effective and resource-sparing intervention.