Perceptions of lights in the absence of light stimuli (photopsias, phosphenes) are usually transient and fairly faint phenomena that are seen most clearly in dark surroundings. There are several types of dynamics, including an abrupt onset and a slow fading, a firework-like spreading, and pulsations. The abrupt-on/slow-off type is suggestive of vitreous tugging whereas other types of phosphene generators may be more difficult to identify. A systematic collection of observations should be useful in this regard. Feedback is welcome.
The location within the visual field may also hold important information. The most common of all photopsia generators, posterior vitreous detachment, typically generates vertically oriented flashes in the temporal field, whereas the retinal tears and detachments tend to generate flashes in other parts of the field, with a horizontal or oblique orientation .Known phosphene generators include the following ([x] identifies a suggested starting point for further study):
New 2016: a refined version of the above display has been included with a host of other symptomimetic displays in a new dynamic visual library. The library has the format of an iPhone/iPad app named Vision Sx.Top
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