The worldwide outbreak of the severe and acute respiratory coronavirus disease (COVID-19) caused by the coronavirus strain SARS-CoV-2 is currently the focal point of discussion due to the suffering this syndrome is causing to humanity. However, the ophthalmological implications of this syndrome have not yet been well described. Both eyes and tears, as portals of entry and sources of contagion, have been the subject of debate by many authors.
A Chinese doctor, Li Wen Liang, became the first physician to become whistleblower to the world about COVID-19. Being an ophthalmologist himself, he has put forward the fact that ocular manifestation could be the first presenting feature of novel coronavirus pneumonia, which should not be ignored, and the possibility of spread of SARS-CoV-2 through the ocular secretions cannot be ruled out. Ocular symptoms commonly appear in patients with severe COVID pneumonia, and it is possible to detect viral RNA from the conjunctival sac of these patients. Apparently, conjunctivitis is not a frequent manifestation of the coronavirus disease in patients with non-severe COVID-19. Despite conjunctivitis generally being a self-limited and benign condition, it is an important route of viral transmission, and therefore, prevention is the most important aspect to remember as ophthalmologists to protect the patients and themselves.
Our eyes have a number of defense mechanisms that help protect against infection, like eyelids that blink to cover the eye and tears that contain immunoglobulin that fight invaders. You blink really easily when even a puff of air goes near your eye. So, if somebody coughs or sneezes near you, you’re likely to close your eyes, whereas your mouth and nose don’t do that. If an infectious person coughs or sneezes in your face, and you breathe in through your mouth or nose, not only are you going to receive a sizable viral dose, it is going to be a fairly direct hit into the airways. Even though the eyes are not a likely way to be infected with the coronavirus, and the pathway from the eyes to the respiratory system is less direct than via nose and mouth, the coronavirus can spread through the eyes, just as it does through the mouth or nose.
Multiple respiratory droplets may be released when an infected person coughs, sneezes, or speaks. These respiratory droplets contact host ocular mucus membranes. Upon contact with an epithelial cell, the virus particle gains entry inside using the SARS-CoV-2 spike (S) glycoprotein, which binds to the cell membrane protein angiotensin-converting enzyme 2 (ACE2). Whether the eyes are one of the preliminary sites of virus transmission from the environment to the lungs via the lacrimal passage, or the virus reaches the eyes in retrograde fashion through the airways passage via the lacrimal system to eyes, is still an issue to look into. The conjunctiva is directly exposed to extraocular pathogens, and the mucosa of the ocular surface and upper respiratory tract is connected by nasolacrimal duct and may share some common entry receptors for these various respiratory viruses.

Eye care during the COVID-19 pandemic
Limiting close physical contact is key to helping reduce the spread of the coronavirus. Symptoms such as fever, cough, and shortness of breath can show up 2 to 14 days after a person is exposed. People with severe infections can develop pneumonia and die from this lung illness. A great deal of information and misinformation has been in the news about COVID-19 since the disease began to spread rapidly in early 2020. Over five million coronavirus cases have been reported worldwide to date, and as we begin to reopen our eye care practices, key questions about the virus and the eye need to be answered. This will determine the best ways to resume patient care safely and effectively.
Some of the questions surrounding us on COVID-19 in eye services are:
1. What is the incidence of conjunctivitis in patients with COVID-19?
2. Can the ocular surface serve as a reservoir of virus possibly transmissible to others?
3. Can the ocular surface serve as a portal of entry for COVID-19 through aerosolized droplets or hand-eye contact?
To answer the above questions, a team performed PubMed, bioRxiv, and medRxiv database searches and analyzed the results of studies in peer-reviewed publications and found the following:
New England Journal of Medicine (2020; 382: 1708-1720) reported that the incidence of conjunctivitis is low (respective range: 0.8% in a study of 1099 patients with confirmed virus examined by non-ophthalmologists to 4.68% in a study of 534 symptomatic patients with confirmed virus examined by ophthalmologists).
Additionally, conjunctivitis may be the first presenting sign of COVID-19, with the other—flulike symptoms—quickly following. The presence of conjunctivitis should be highly suspicious for the presence of the COVID-19 virus. The examiner should treat these patients as highly infectious, with very high likelihood that they are shedding virus from their ocular surface. However, patients without conjunctivitis, even if they have other COVID-19 symptoms and should also be treated as highly infectious, are unlikely to harbor viral RNA on their ocular surface.The ocular surface may also be protected by the ‘good’ bacteria living there and comprising a unique microenvironment called the ocular microbiome, the microbiome on the ocular surface and its effects on the eye’s immune homeostasis and defense against pathogens.
The conjunctivitis found in these patients is a typical mild to moderate viral follicular conjunctivitis with conjunctival injection and watery discharge. Conjunctivitis can be either the first presenting sign of COVID-19, or present later in the disease course, with a duration of four to seven days. The main complaints of these patients are redness, tearing, discomfort, foreign body sensation, and discharge.
The ocular surface being a portal of entry for COVID-19 virus, the potential exists, and although the ocular surface has receptors that the virus uses to initiate its attachment to a human cell, other components of the ocular surface may prevent viral attachment and entry. The virus may potentially travel from the ocular surface to the respiratory tract mucosa via the nasolacrimal duct.
The infectivity of the ocular secretions of the COVID-19 infection should not be ignored. Due to close doctor-patient distance in ophthalmic practice, social distancing is virtually impossible, with greater chance for transmitting SARS-CoV-2 virus by droplets, aerosols, ocular secretions, and contaminated ocular instruments. The clinicians are advised to assume a patient has COVID-19 if they have conjunctivitis and that they will be shedding virus from their ocular secretions, and are, therefore, contagious. In this case, physicians will need more than hand sanitizer and a mask.
They should wear gloves when examining such patients and assume that symptomatic patients have virus in their nasopharyngeal secretions, and that the virus likely will be aerosolized when they speak. Therefore, wearing an N95 mask and tight-fitting goggles is essential. Examiners should also instruct patients not to speak when they are in close proximity to the physician or examiner.

1. María A Amestyet all. COVID-19 Disease and Ophthalmology: An Update. Ophthalmol Therapy.2020 Sept; 9(3): 1-12.
2. Guan W-J, Ni Z-Y, Hu Y, et al. Clinical characteristics of coronavirus disease 2019 in China. N Engl J Med. 2020; 382(18): 1708-1720
3. Zhou Y, Zeng Y, Tong Y, Chen CZ. Ophthalmologic evidence against the interpersonal transmission of 2019 novel coronavirus through conjunctiva.medRxiv. Preprint posted online February 12, 2020
4. Sun CB, Wang YY, Liu GH, Liu Z. Role of the Eye in Transmitting Human Coronavirus: What We Know and What We Do Not Know. Front Public Health. 2020; 8: 155
5. New England Journal of Medicine (2020; 382:1708-1720).

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