Our eyes deserve special care during the Covid-19 pandemic.

By Fábio de Oliveira, from Agência Einstein - Avoiding touching the eyes has become a mantra during the Covid-19 pandemic, as they can be a route for the novel coronavirus to enter the body. The germ is capable of causing conjunctivitis, as shown in a study published in the scientific journal. Journal of Medical VirologyConducted in China, the study evaluated the tears and conjunctival secretions – the mucous membrane that lines the sclera, the white part of the eye – of 30 patients with pneumonia resulting from infection with the virus. The samples were analyzed using the RT-PCR test, which diagnoses infection by Sars-Cov-2. In the only patient with conjunctivitis, the result was positive for the presence of the microorganism in the collected material. 

Tear secretions participate in the eye's cleaning system, which begins with the mechanical act of blinking. Humans blink 15 to 20 times per minute. "It's a way to lubricate the ocular surface and eliminate any substance or microorganism that might land on the eyes," explains ophthalmologist Adriano Biondi, from the Albert Einstein Israelite Hospital in São Paulo. The tear is drained into the lacrimal canal, goes to the lacrimal sac, and then to the nasal mucosa until it reaches the pharynx. Its journey ends in the throat. It's the same path the virus travels along. 

Tear discharge can be found on towels and bed linens, for example. But it is still unclear how long the virus remains infectious under these conditions.

Home office

There are ways to increase protection. Those working from home almost always spend more time in front of a computer or cell phone screen. This interferes with our ability to blink. "When you look at a screen, there's a change in the normal physiological response responsible for eye cleaning," explains Biondi. The eye becomes more open and static, and blinking is up to three times less. The result is dryness, characteristic of computer screen overuse syndrome. Its symptoms include burning, redness, blurred vision, and eye fatigue. An incorrect prescription for glasses also contributes to this. 

The eye dries out very quickly. It has a hydrating film, the tear film. This film has layers. The outermost layer is made of fat, responsible for creating a surface tension that "holds" the tear in the area. The second layer is the aqueous part, consisting of water, enzymes, electrolytes, and proteins, which nourish the cornea. "That's where viruses circulate," says Biondi. The third layer is in contact with the surface of the eye and is called the protein layer. Eye cells produce proteins with an electrical charge that attracts and holds water in the area. "The three work in harmony," reports the ophthalmologist. If a problem occurs, such as blepharitis, inflammation of the eyelid, there is instability in the tear film – it disappears in seconds. The eye becomes irritated, creating an opening for viruses because the natural cleaning system is not working properly. This also applies to viral conjunctivitis, not just SARS-CoV-2. 

A necessary pause

To prevent eye strain from exhausting work in front of a computer, ideally, every 20 minutes, take a 1-minute break away from the screen. "Look into the distance, blink more, and drink a glass of water for eye rehydration," advises the ophthalmologist. Looking at the horizon or anything distant rests the eyes – while looking at something close has the opposite effect. This is because humans have predator eyes: they are parallel and adapted to see prey from afar, just like an eagle's. With prey animals, the story is different. "Ducks and chickens have laterally positioned eyes to see who is coming from behind and escape," says Biondi.