When you close your eyes, you might be able to see them. Or when you rest your gaze on a white wall or a blue sky.
Strange formations, either dark or transparent, floating around on the retina. When you try to focus on them, they slip away, moving up, down, or sideways.
These are called floaters.
"They aren't located on the retina itself, but in the clear, jelly-like substance that fills the inside of the eye," says Rigmor Baraas, professor at the University of South-Eastern Norway.
But why are they there? Are they caused by eye damage from too much sun exposure without sunglasses? And can we ever get rid of them?
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This is what floaters, or muscae volitantes, can look like for some people.(Image: Shutterstock / NTB)
For others, they may look like floating shadows, or debris in the eye.(Image: Shutterstock / NTB)
How common are they?
The scientific name is Muscae volitantes.
If you suddenly experience an increase in the number of floaters, you should see an optician or ophthalmologist, says Rigmor Baraas.(Photo: University of South-Eastern Norway)
One study shows that 76 per cent of Americans experience floaters in their field of vision.
Baraas does not know how many people in Norway have them.
"But it's not uncommon," she says.
What are they?
So what exactly are these floating spots?
"They are small clusters of cells or strands of protein," says Baraas.
They are located inside the vitreous body of the eye, which is the jelly-like substance at the back of the eye.
When light enters the eye through the lens, specific cells on the retina are activated. As floaters move within the vitreous body, they cast shadows on the retina, creating the odd shapes many people see.
Such as small spots, threads, transparent worms, and cloud formations.
Here you can watch a video about floaters from TED Ed:
(Video: Michael Mauser, December 2014: What are those floaty things in your eye? Retrieved from TedEd.)
Why do we get them?
For most people, floaters don't cause any real trouble.
