WHAT IS SCHEERER'S PHENOMENA
If you every stare at a bright blue sky and feel you are seeing little white "dots" darting in curves in your vision, you are experiencing Sheerer's Phenomena.
This visual phenomenon occurs because the eyes capillaries from the arteries are very small, allowing only one red blood cell or white blood cell to pass at a time. These capillaries in your eyes dip down towards the level of the eye's photoreceptors. When a white blood cell passes close to the photoreceptors in carries some of this blue light along with it allowing your to see these darting lights.
These darts of light will increase during exercise and decrease when blood flow decreases.
Next time your at the beach on a clear blue day see if you can see your own white blood cells. But no staring at the sun!