“The only part of the body that has no blood is the cornea of the eyes,” reads a graphic posted on Facebook. “It receives oxygen directly from the air.”
Blood carries oxygen and nutrients to the cells, and removes carbon dioxide and other waste products.
The cornea is the clear part of the eye, at the front. It is dome-shaped, which allows it to bend light. This helps the eye to focus.
But does the cornea have no blood, and instead get its oxygen from the air? We checked.
You can’t see through blood
According to an article on the US National Center for Biotechnology Information website, the cornea can’t contain blood because it must remain transparent – otherwise we would be blind. Blood is opaque, and we can’t see through it.
The cornea gets its nutrients from our tear fluid, as well as from the aqueous humour. The aqueous humour is a clear, slightly alkaline liquid in the space in front of the eye’s iris and lens “and the ring-like space encircling the lens”.
A diagram by the West Texas A&M University in the US shows these different parts of the eye.
Contact lenses can reduce oxygen in cornea
The cornea does not contain any blood. But does it get its oxygen from the air?
A 2010 study about oxygen distribution in the human eye found that when our eyelids are open the oxygen levels near the inner surface of the cornea are produced by the cornea consuming oxygen from the air.
So the cornea does get its oxygen from the air. This has led to concern that wearing contact lenses could limit the amount of oxygen the cornea receives.
The US University of Michigan Health website says that a common complication of wearing contact lenses, especially if they are worn for a long time, is hypoxia – lack of oxygen – of the cornea.
“The cornea has no blood supply of its own, so it gets oxygen only from tears and directly from the atmosphere. A contact lens reduces the oxygen supply to the cornea, making the cornea swell.”
It warns that wearing contacts overnight can further decrease the amount of oxygen that gets to the cornea.
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