To the editor: In urban area of industrial countries, the ocular surface is exposed
daily to intense burden of particulate matter, ozone, carbon monoxide, nitrogen dioxide
(NO2) and sulfur dioxide produced by fossil fuel. Air pollution is a causative factor
for various ocular surface complaints such as eye redness, irritation and blurring
of vision, as well as various ocular diseases such as meibomian gland disease and
dry eye disease, vernal keratoconjunctivitis, allergic conjunctivitis, retinal vein
and artery occlusion, and glaucoma.1–4 Putative pathophysiology of air pollutants
is mediated by oxidative stress in ocular tissues exposed to atmospheric changes involving
damage of cellular DNA, membrane lipids peroxidation, inactivation of receptor protein
and enzymes, and finally cells apoptosis and autophagy mediated by autophagosome.3
5 Similarly, air pollutants promote neurotoxic and microvascular effects impacting
on cardiovascular diseases as well as glaucoma and retinal vascular diseases.2 6 7
Since 8 December 2019, the world has been confronted by a viral pneumonia pandemic
caused by the coronavirus named Severe Acute Respiratory Syndrome (SARS-CoV-2) or
Coronavirus Disease 2019 (COVID-19). Initially described in Wuhan, Hubei, in the Peoples
Republic of China, the movement of people and freight through tourism and commercial
airline flights contributed to the spread of the global pandemic, causing millions
of cases and tens of thousands of deaths. The local authorities responded quickly
to promulgate quarantine status of epicentres such as towns, popular districts, production
plants and other gathering places. Consequently, the reduction of human activities
has impacted on greenhouse gas emissions from industry, tertiary services, mass transits
or individual car circulation. NASA’s Aura satellite described a marked reduction
of nitrous oxide (NO2) across China from 1–20 January 2020 (before the quarantine)
to 10–25 February (during the quarantine).8 9 According to NASA scientists, the reduction
in NO2 pollution was first apparent near Wuhan, but eventually spread across the country
and around the world. A similar NO2 decrease across Europe, China and India were identified
by Copernicus Sentinel-5P satellite, from the European Union Copernicus programme,
during quarantine.10 11 Globally, an NO2 decrease of 40%–50% over major cities across
Asia, Europe or North America were measured following the decrease of global economy
due to coronavirus epidemic (figure 1).8 10 11 The impact of the global reduction
of air pollution during SARS-CoV-2 pandemic could positively affect all the biodiversity
of Earth, involving the slowdown of climatic change and the quality of freshwater.
Therefore, the strong efforts of the international community to contain the COVID-19
epidemic may also have indirect health benefits by lowering the impact of air pollution
on ocular diseases. Even if SARS-CoV-2 involves conjunctivitis and external ocular
infections,12 there are not yet published data describing the effects of a reduction
of air pollutants on the ocular surface during the quarantine period, and a putative
decrease in some ocular complaints—individuals being at home and less exposed to pollens
and atmospheric pollutants. However, all activities soliciting the near vision and
accommodation were particularly increased during quarantine such as videogames, television,
tele-working, reading and others activities in smartphone, putatively generating dry
eye symptoms and visual fatigue.13 Also, it should be noted that a large number of
doctors accidentally acquired coronavirus infection by contact with oropharyngeal
fluids, but also tears and conjunctival secretions of patients14—particularly for
patients with conjunctivitis.15 Furthermore, recent data highlighted that ocular symptoms
could occur about 10–15 days after systemic contamination, with a low positivity rate
of reverse transcription-PCR in tears and conjunctival samples (ie, conjunctival swab
or/and scrapping).16 17 SARS-CoV-2 patients without any ocular symptoms could also
excreted SARS-CoV-2 in tears.18 Even if SARS-CoV-2 is an enveloped virus surviving
a few hours or days on dry inert surfaces, the contaminated surfaces of ophthalmological
consultation rooms are an established route of SARS-CoV-2 spreading.19 Thus, ophthalmologists
are mainly concerned by an aerosol transmission, working in confined spaces at few
centimetres from the faces of their patients, and a transmission by contact with tears
or contaminated surfaces. Considering the contagiousness of the SARS-CoV-2, personal
protective equipment is necessary in daily clinical practice: gloves and filtering
face piece respirators (FFP2 or FFP3 masks) for the ophthalmologist and surgical facemasks
for the patient.20 A plexiglass barrier (protective shield) between patient and ophthalmologist
is as additional salient approach during close clinical and paraclinical examinations.21
Those preventive measures against SARS-CoV-2 will increase the duration of consultation,
which will increase the waiting list for patients—that is already long and that may
further delay medical treatment.22 In conclusion, even if individuals are less exposed
to air pollutants and environmental allergens during quarantine weeks, SARS-CoV-2
seems to be a foe both for ophthalmologists—with a risk of infection through contact
with eye secretions of patients—and for patients—with a delay in their medical management.
The SARS-CoV-2 will probably upset ophthalmological practices during the forthcoming
months or years.
Figure 1
The decrease of global air pollution following the Severe Acute Respiratory Syndrome
Coronavirus 2 (SARS-CoV-2) pandemic (satellite images from NASA and European Space
Agency).8–11