Phosphene

Phosphenes ( from Greek φῶς "light" and φαίνειν "appear" ) are light perceptions, which are not produced by light but by other stimuli to the eye, the optic nerve or the visual cortex in the brain.

Phosphene can be generated by pressure on the eyeball ( Druckphosphene ), since in this case the membranes are stretched and the next influx of sodium ions, a depolarization will be produced that is perceived as an irritant. Wherein phosphene tonometry is calculated from the force which is necessary to generate a phosphene, closed on the intraocular pressure.

Also direct electrical stimulation or the influence of electromagnetic fields can produce phosphenes ( magnetophosphenes ). The latter happens for example in the transcranial magnetic stimulation (TMS ), and can be utilized for diagnostic tests.

Phosphenes also occur in pathological changes in the brain such as migraine attacks, and can occur as a side effect of medication.

In the 18th century were at times " phosphene parties " popular, in which the participants sat in a circle, is bordered on the hands and ran supplied by the group of an electrostatic generator power to experience so Phosphenwahrnehmungen.