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I had a hard climb a week ago. I got so tired then any time I closed my eyes I saw these lights inside my head. I see these lights almost every time that I run fast or some thing like that. What are they and where do they come from?

schematic representation

Here is a picture I drew using Photoshop ;)

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I sometimes see similar “lights”, too. Although of somewhat different shapes. –  winerd Jun 15 '13 at 19:44
    
interesting that you see hexagonal shapes. Hexagons often appear in 2D sensory processing due to its relation to sphere packing. –  Memming Nov 5 '14 at 1:48

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This is a common phenomena which most of us come across. Seeing flashes of light, stars and other shapes in the eyes occur when the body goes through stressful activities. For example while you are climbing the blood flow will be more to other prominent parts like hands and lower waist so brain and eyes will get less supply of blood as well as nutrients. Hence those flashes or stars are visible to us. This phenomena is called "Phosphene" and a phosphene is a phenomenon characterized by the experience of seeing light without light actually entering the eye.

Wikipedia/Phosphene gives an explanation for occurrence of Phosphenes:

Phosphene is "seeing stars", from a sneeze, laughter, a heavy and deep cough, blowing of the nose, a blow on the head or low blood pressure (such as on standing up too quickly or prior to fainting). It is possible these involve some mechanical stimulation of the retina, but they may also involve mechanical and metabolic (such as from low oxygenation or lack of glucose) stimulation of neurons of the visual cortex or of other parts of the visual system. enter image description here

So seeing flashes of light can be due to:

  1. Blood shifting.
  2. Low blood sugar(causes weakness).
  3. Head trauma.
  4. Headache.

So to summarize this thing, we should have enough nutrients, water supply to the body whenever we come across stressful activities. Phosphenes are temporary stuff which do not harm eyes.

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It could be posterior detachment of the vitreous humor. Stress on the optic nerve caused by motion of the vitreous humor inside the eye can lead to the sensation of lights. And since the nerve is circular, you see a pattern of circular light. Normally its not serious, and many people experience it as age progresses. If you are not hydrating well during your climbing that might also be aggravating it. To be safe you should have an eye doc check you out though since there is slight risk it could lead to retinal detachment.

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This is very much like calling out "Zebra!" when you hear hoof beats (unless you happen to live on the grasslands of eastern and southern Africa. In that case, it's more like calling out "Caribou!" –  anongoodnurse Jun 6 at 0:43
    
@anongoodnurse I'm also a climber, a runner, experience dehydration and on occasion experience the same light sensations when I press my eyelids tight suddenly or turn my head suddenly left to right at night. And this is what my doctor diagnosed. So what are you suggesting might be the issue otherwise besides grassland animals? –  docscience Jun 6 at 5:17
    
What your doctor said doesn't carry much weight with me. They and I are of differing opinions. I don't think I could be any clearer expressing my opinion. If every time someone who exerted themselves saw lights it turned out to be a pulling on the retina, opthalmologists would be more common than dirt. –  anongoodnurse Jun 9 at 5:41

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