Cor(o)nea-virus

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Written by Eef van der Worp, published in his Eef@online series at Linkedin 23-03-2020

Pretty much every news item these days is related to the topic ‘virus’. In our profession as eye care providers we are typically mostly worried about cornea-viruses, but that is different now.

At War

While we seem to be at war with a virus in the world-wide pandemic, it is weird to realize we are at war with a non-living creature. Viruses are pretty much non-living packages of DNA; they cannot live outside of a living cell. So the virus invades our cells, uses it – and goes on to the next cell. It cannot survive without ‘us’ basically. That is why the transmission of this virus is mostly via a direct way – e.g. via droplets that are sneezed or coughed on to the next person directly.

No Extra Risk

When you think about contact lens safety and corneal infections, viruses are actually not the first ones on our minds. The reason is exactly what is described above: a virus cannot live outside the human body.

Bacteria can, and Acanthamoeba (free-living protozoa) can too. So, if we have one or a few bacteria in our contact lens case with purified water then these ‘animals’ (literally, and by figure of speech) can reproduce dramatically fast. Rabbits have the name for it - but believe me these micro-organisms are the worldchampions reproducing.

You can see I miss my daily shot of sports coverage here, by the way.

Eef van der Worp

Eef van der Worp is an educator and researcher, who received his optometry degree from the Hogeschool van Utrecht in the Netherlands (NL) and has since worked in different positions at the school

Contact Lens Related?

That’s why we don’t see – relatively speaking – much more corneal virus infections in lens wearers compared to non-lens wearers. For bacterial infections, and even to larger degree for Acanthamoeba infections, the opposite is true: these are more prevalent in contact lens wearers. The latter case (Acanthamoeba) is in fact almost exclusively to contact lens wearers. Not something to be proud of. This has to do with the involvement of tap water in the lens care regimen. If an Acanthamoeba trophozoite is present and the lens gets stored in tap water overnight, then these parasites can increase substantially in number so that the next morning when the lens is applied to the eye, millions of micro-organisms are introduced to the ocular surface.

That is why the general rule, for any contact lens regimen including rigid corneal and scleral lenses, is: no tap water!

Defense

Normally the defense mechanism of the eye is pretty good, with the epithelium and Bowman’s layer as first lines of defense if intact. But the combination of a compromised anterior ocular surface, with an overload of micro-organisms… that is not a favorable one. But with viruses, we typically don’t have the overload of overnight growth as we see with bacteria and Acanthamoeba - and viruses are in that regard relatively less of a worry. Wish we could say the same about the Corona-virus and our general health.

 

This series Eef@online series is kindly supported by an educational grant from Contamac Ltd – Empowering Your Vision

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