A Covid-19 infection would increase the risk of occlusion of the eye

• American researchers have just established that an infection with Covid-19 could potentially increase the risk of developing ocular occlusions.

• These conditions could develop up to several months after contracting the coronavirus.

• These occlusions, a kind of stroke of the eye, can cause vision problems.

Is the long list of symptoms and side effects of Covid-19 getting longer?

And touch our eyes?

Maybe.

Patients who have contracted the coronavirus may have an increased risk of developing an ocular occlusion, a type of stroke of the eye, according to a study published on April 14 in the scientific journal

​.

What is an ocular occlusion?

What are the causes of this condition?

Are the conclusions of this study making the link with Covid-19 plausible?

takes stock.

An increase in the incidence rate

If scientists are still trying to unravel the mysteries of the coronavirus, they have already been able to establish that it is notably associated with increased risks of obstruction of blood vessels in the body.

“Covid-19 is associated with systemic vascular damage;

however, the risk to the retinal vasculature is not fully understood,” note the study authors, a team of California researchers specializing in sight loss research.

To shed light on the risk of developing clots in the artery or veins of the retina – the nerve tissue at the back of the eye that receives images and sends them to the brain – scientists have compiled data on a large cohort of 432,515 participants who contracted Covid-19.

According to their findings, Covid patients would have a higher risk of developing an ocular occlusion.

In the six months following the contamination, 65 patients of the cohort had a retinal vein occlusion (RVO).

A relatively low number, but which still reflects an increase in the incidence rate of 54% compared to the rate of infection in the general population excluding Covid-19.

They also report a 35% increase in cases of central retinal artery occlusion (CRAO).

A kind of eye stroke

But what is an occlusion of the eye?

“An OACR is usually caused by an embolus.

This can for example be a piece of clot that has migrated from the atrium of the retina.

The clot will then obstruct the central artery and deprive the retina of oxygenation, describes Professor Gilles Renard, scientific director of the French Society of Ophthalmology and former head of the ophthalmology department at the Hôtel-Dieu.

In this, we can say that it is a kind of stroke of the eye.

Originally, the eye is a piece of brain, and in case of ischemia – the insufficiency or the stoppage of the blood circulation of an area –, after a few minutes, there is damage.

And when the vision is altered, it is final.

In the event of a stroke, it's the same problem: we have a few minutes to try to re-oxygenate the area,

and a maximum of a few hours to try to unclog the clogged artery”.

Another factor of the OACR, “Horton's disease, which is characterized by damage to the aorta, which affects both the temporal artery and the central retinal artery”.

RVO is triggered by other risk factors, “in particular diabetes and high blood pressure, which are also risk factors for a severe form of Covid-19”, underlines Professor Renard. .

When it is the retinal vein that is affected, "with anticoagulant treatment or even laser intervention on the areas whose blood circulation has been hindered because of the occlusion, we manage to stabilize things in a certain number of cases", reassures the professor of ophthalmology.

Causality not established

By looking a little more closely at the results of the study, with 65 cases of occlusion of the eye in such a cohort, what credence should be given to these conclusions?

The figures observed, certainly higher than in the general population but still quite low, could be due to chance or to known risk factors for these conditions.

"Based on such a large cohort, I wonder about the reliability of the causality mentioned," says Professor Renard.

However, we know that Covid-19, like certain anti-Covid vaccines, are intravascular coagulation factors, he explains.

The conclusion that a Covid infection leads to coagulation of the central artery or a vein of the retina is not aberrant”.

On the other hand, "it is not impossible that the correlation is not as exact as what the authors of the study would like", he adds.

The study also does not make it possible to prove that Covid-19 is the cause of these cases of ocular occlusion, recognize the researchers, who believe that broader studies on the question are necessary.

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