Phosphene is a term used to describe the perception of light without an actual light source. It is pronounced /ˈfɒsfəni/ in IPA phonetic transcription. The spelling of "phosphene" can be understood by breaking it down into its Greek roots: "phos" meaning light and "phainein" meaning to show. The "ph" spelling is also characteristic of words borrowed from Greek. Overall, the spelling and pronunciation of "phosphene" reflects its origin in Greek philosophy and science.
A phosphene refers to a transient visual perception of light or color in the absence of an external light source. It is a subjective experience that occurs due to the activation of the visual system without any corresponding visual stimulus. Phosphenes are commonly described as glowing, flickering, or shimmering patches, dots, or lines that appear in the visual field.
The phenomenon of phosphene can be induced by various factors, such as mechanical pressure on the eyeballs, electrical stimulation of the visual cortex, or even strong sneezing or coughing. Applying gentle pressure on closed eyelids, for instance, can trigger mechanical stimulation of the retina and lead to the perception of phosphenes. Similarly, stimulating the visual cortex through transcranial magnetic stimulation (TMS) can also elicit phosphenes. Phosphenes can vary in intensity, size, shape, and duration.
Phosphenes are thought to arise from the excitation of neurons in the visual system, either at the level of the retina or in higher visual processing centers. Although they do not represent actual external light stimuli, phosphenes can be perceived as real visual experiences. They have been utilized in different fields, such as medicine, neuroscience, and art, for studying visual perception, simulating visual experiences, and creating visual illusions.
A subjective sensation of light produced by pressure upon the eyeball.
A practical medical dictionary. By Stedman, Thomas Lathrop. Published 1920.
The word "phosphene" comes from the Greek roots "phos" meaning "light" and "phainein" meaning "to show" or "to appear". Therefore, it can be understood as "light appearing" or "light showing". This term was coined in the 19th century by combining these Greek roots to describe the phenomenon of seeing light or flashes without any corresponding external source of light.