We’ve all experienced it – when you rub your eyes too hard, or press your fingers against them, your vision is filled with an array of colours either as spots of brightness or strange twisting spirals.
Well, there’s actually a scientific term for the colourful “stars” you see in your vision, called phosphenes: this is when your eyes experience the sensation of light, without light actually entering them.
There’s lots of different ways you can see phosphenes; if you accidently hit your head, they could come as flickering bright white light, and pressing your eyes shut tightly will bring “spots” to your vision. The experience of pressing your eyes and seeing colours is “pressure phosphenes”.
Why do we experience this?
Our eyeballs possess a neuron called a retinal ganglion cell, which receives visual information from the photoreceptor cells in the retina. This is what contributes to our vision – the retinal ganglion cell receives information from the photoreceptor cells being stimulated by light entering the eyes.
These retinal cells can also be activated by applying pressure, which gets them working in a similar way to when they’re activated by light.
Essentially, you’re tricking your nervous system into thinking your eyes are open.
You can also experience phosphenes when you have a migraine, though scientists aren’t certain why this is the case. It may be the result of electrical activity in certain parts of the brain.