The blue arcs: An electrifying visual phenomena

The proliferation of red LEDs on electronic equipment of every sort has made it easy to observe one of the more interesting entoptic phenomena. Normally, visual experiences are caused when light stimulates the retina, the network of nerve cells at the back of the eye. Entoptic phenomenon are produced when something other than light stimulates the retina. Thus, if you gently poke the side of the eye with your lids closed, you will see a spot of light on the opposite side of the visual field. This so-called pressure phosphene is caused by mechanical stimulation of nerve cells.

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