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An artist's representation of how some people may see phosphenes by retinal stimulation. A phosphene is the phenomenon of seeing light without light entering the eye. The word phosphene comes from the Greek words phos (light) and phainein (to show). Phosphenes that are induced by movement or sound may be associated with optic neuritis. [1] [2]
The FWHM of the seeing disc (or just "seeing") is usually measured in arcseconds, abbreviated with the symbol (″). A 1.0″ seeing is a good one for average astronomical sites. The seeing of an urban environment is usually much worse. Good seeing nights tend to be clear, cold nights without wind gusts.
The observer described them as being similar to "luminous balls seen in fireworks, with initial tails fuzzy and heads like tiny stars". The other observer who was given one exposure lasting three seconds long, reported seeing 25 to 50 "bright discrete light, he described as stars, blue-white in color, coming towards him". [8]: 596
The Triangulum Galaxy (M33) is a difficult averted vision object and only visible at all if it is higher than 50° in the sky. The globular clusters M 3 in Canes Venatici and M 92 in Hercules are also visible with the naked eye under such conditions. Under really dark sky conditions, however, M33 is easy to see, even in direct vision.
In teichopsia, migraine sufferers may see patterns that look like the shape of the walls of a star fort. As the scotoma area expands, some people perceive only a bright flickering area that obstructs normal vision, while others describe seeing various patterns. Some describe seeing one or more shimmering arcs of white or colored flashing lights.
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It is light-sensitive and communicates visual messages to the brain. If the retina detaches, it moves and shifts from its normal position. This can cause photopsia, but can also cause permanent vision loss. Medical attention is needed to prevent vision loss. Procedures may include laser treatment, freezing, or surgery.
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