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Whenever I get ready to go to sleep, I shut the lights off and lay my head down on my pillow. Once the room is dark, if I shake my head from side to side while laying down, I see white flashes of light. Why does this happen? Is it normal? I am 18 by the way and this only happens at night while it's all dark and when I'm laying down.
Alrighty. Here we go, to the best of my knowledge. I hope this makes sense. This is usually the case for "seeing light" because of movement.
Your skin is equipped with various receptors. If you touch your skin, pressure receptors signal "something is touching me". But let's say you shine a light on your skin. Does your skin let you "see" the light waves? No. It lacks the proper receptors. The only thing you could detect is maybe some heat given off by a powerful light.
Inversely, your eyeballs are equipped with photorecepters that detect light stimulus (but not touch). So, when stimulated by movement, or more accurately, pressure, the only signal they are capable of sending to the brain is an action potential that we translate into what we know as light. They cannot send a "hello there, your vitreous humor is pressing against me and I feel it" signal.
No matter the stimulus (light, pressure) the response is the same for these photoreceptors.
So basically... You see light because you are mechanically stimulating photoreceptors that can only detect light.
Is that what you were looking for? I asked my Anatomy and Physiology teacher that two years ago and that is generally what he said. It is easier to explain with hand gestures!
I think it may just be a trick of the brain. You shake it, along with your eyeballs, when you shake your skull around so you think you're seeing flashes of light.
You should probably stop shaking your head like that.
These brief streaks of light are usually seen especially at night or when the head or eyes are turned. These flashes are caused by the vitreous pulling on the retina. In some instances these flashes can be the signs of retinal tearing and can result in retinal detachment and blindness if not treated properly.
The white light is caused by the brain gently knocking against your skull. Its not an action we do in every day life, there's a reason for that. the bigger question is: WHY?