Ever rubbed your eyes so hard that you've been left seeing stars?
They mightn't always be five-pointed shapes, but appear as fireworks, speckles, or flashes of colour.
Well, if the answer is yes, and you've always wondered what exactly is happening to spark such illusions, then read on.
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What is the sensational called?
You might be surprised to learn that there isn't actually a technical term used to describe applying such a level of pressure to the eye that you start seeing pictures and graphics.
But according to experts at BBC Science Focus, the splashes of coloured light that we see after pressing our eyes are known as 'phosphenes'.
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And while you might think there's sorts of phenomena that were named as recently as the 20th century, they were actually first reported as long ago as the Ancient Greeks were around.
Philosopher and early neuroscientist Alcmaeon of Croton once wrote in the 5th century B.C. of the vision experienced following a blow to the head: "The eye obviously has fire within it, for when the eye is struck fire flashes out."
What actually causes it?
When you rub your eyes aggressively using your fingers or hands or push too hard into your sockets using the ball of your wrists, pressure is created within the eyeball.
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This pressure activates things called ganglion cells in the retina, in the same way that light does when we're looking around.
Being unable to tell the difference between simply seeing, and activating these cells, the brain interprets your vision as though you're actually seeing light from the outside world.
Explaining it further Angie Wen - a cornea surgeon at New York Eye and Ear Infirmary of Mount Sinai - explained: "[Sometimes] we see light that actually comes from inside our eyes or from electric stimulation of the brain rather than from the outside world.
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"These bursts of seemingly random intense and colourful lights are called phosphenes, and appear due to electrical discharges from the cells inside our eyes that are a normal part of cellular function."
What do most people see?
As we say, not everything graphic you see when you rub your eyes is star-shaped.
In fact, the most common phosphenes are described by those who commonly experience them are diffuse blobs of different colours.
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The more the eyes are rubbed, the more that these images seem to move and dissipate.
Other types of phosphenes are scintillating, and move rather quickly across your vision in patterns, which are often similar to psychedelic paintings.
According to the BBC, these 'probably reflect the organisation of cells higher up in the visual system'.
This is because the major hallucinogens also affect the visual system in the same way.
Other people might be intense flashes of a sky-blue light.
Apparently, the latter could indicate that the eye has been pressed for too long, and therefore you should refrain to minimise the risk of damaging the eye any further.
Rhianna Benson