Can we get covid-19 through the eyes?

Cristina Peris Martínez, Fisabio

The first doctor in the world to die from covid 19 was the Chinese ophthalmologist Li Wenliang: since its inception, this medical specialty has been closely linked to the pandemic. Though the main route of contagion of covid-19 is respiratoryIt can also be transmitted by fomites through human contact through contaminated hands and surfaces.

Less well known is the viral load present in the human tear, as well as in the corneal cells and the conjunctival mucosa. The mechanism of entry of coronaviruses into cells occurs through the receptor for angiotensin converting enzyme 2 (ACE2). This receptor for coronaviruses and SARS-CoV-2 is also present in ocular cells, and this is the reason that these patients may also have ocular manifestations.

Therefore, the transmission of SARS-CoV-2 through the ocular surface and the tear is feasible. Aerosols infected by the virus come into contact with the ocular surface and subsequently the respiratory system through the duct. Anatomically, the conjunctival (eye) mucosa and the respiratory mucosa are connected through this duct.

What are the ocular manifestations of covid-19?

SARS-CoV-2 is causing a great impact around the world and its clinical manifestations are still not fully understood.

Most of the clinical investigations have focused on respiratory manifestations. Nevertheless, there is a growing body of evidence of ocular manifestations.

Some caused by the virus itself and others derived from the pandemic, either due to changes in life habits or derived from the long stay of patients in intensive care units (ICU), where they can be from 3 to 6 weeks with assisted ventilation and in the prone position.

In> cases of bilateral optic disc papilledema and retinal hemorrhages which may be associated with a hypercoagulable state. Also a Increased intraocular pressure due to periorbital edema due to direct compression of the eye and orbit (orbital compartmentalization syndrome) due to long periods in the prone position (16 hours a day).

On the other hand, the long periods of confinement and the use of mandatory masks have meant a increased incidence of dry eye and other ocular surface diseases.

The ocular manifestations produced by the published SARS-CoV-2 itself are highly variable and include conjunctivitis, episcleritis, dry eye, foreign body sensation, itching, blurring of vision, conjunctivitis and photophobia.

The most frequent in the conjunctivitis or inflammation of the conjunctival mucosa, which can even present as an early sign for the diagnosis of covid-19. The incubation period of the virus ranges from 5 to 14 days. It can occur in isolation, as a prodrome of respiratory infection and even appear after the onset of systemic symptoms. The time of evolution of the ocular clinic is also variable. The prevalence of ocular infection is very low (0.8-9.4%, depending on series). In a meta-analysis they concluded that conjunctivitis may be associated with a more serious form of the disease.

In addition> paralysis of the nerves that are responsible for innervating the muscles of eye movements. Isolated cases of optic neuritis are also appearing. In addition to the cornea, SARS-CoV-2 viral RNA has also been detected in the retina of deceased COVID-19 patients.

Through optical coherence tomography and fundus examination, hyper-reflective lesions at the level of ganglion cells and plexiform layers, as well as subtle cotton wool spots and microbleeds along the retinal arch, possibly related to covid-19. Despite everything, the debate continues.

What can we do to prevent it?

Some publications have shown that the eyes (the conjunctival mucosa) are a gateway for the virus into the body and a potential source of infection.

Although the virus has been isolated in tear secretions of patients without conjunctivitis, the risk of ocular transmission in these subjects seems negligible, since the viral load is much lower than in the respiratory mucosa.

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Despite being in a state of pandemic for more than 10 months, we do not know exactly the behavior of the infection. But you need to be very cautious. In this way, continuous hand washing is essential and avoid touching and rubbing our eyes. This measure is especially important in contact lens wearers (scrupulous hand washing and drying before and after contact lens wear).

In clinical practice, in addition, ophthalmologists use protective glasses, screens in slit lamps and use of topical medication in single doses.

Cristina Peris Martínez, Medical Director, Medical Ophthalmology, Fisabio

This article was originally published on The Conversation. Read the original.

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