Phosphenes
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Phosphenes
Phosphenes (/ˈfɒs.fiːnz/, from the Greek words phos, meaning "light", and phainein, meaning "to show") are a phenomenon characterized by the experience of seeing light without light actually entering the eye. This sensation can be caused by various stimuli, including mechanical, electrical, or magnetic stimulation.
Causes
Phosphenes can be directly induced by mechanical, electrical, or magnetic stimulation of the retina or visual cortex as well as by random firing of cells in the visual system. They have also been reported by individuals undergoing magnetic resonance imaging (MRI).
Types
There are several types of phosphenes:
- Mechanical Phosphenes: These are induced by applying pressure to the closed eye. The pressure mechanically stimulates the cells of the retina and creates an impression of light.
- Electrical Phosphenes: These are induced by the application of electrical stimulation to the surface of the visual cortex or the retina.
- Magnetic Phosphenes: These are induced by the application of strong magnetic fields to the head, such as those produced by an MRI machine.
Related Terms
- Entoptic Phenomena: These are visual effects whose source is within the eye itself. Phosphenes are a type of entoptic phenomenon.
- Visual Cortex: This is the part of the brain responsible for processing visual information. It can be stimulated to produce phosphenes.
- Retina: This is the light-sensitive layer of tissue at the back of the inner eye. It translates light into nerve signals that are sent to the brain.
See Also
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