Have you seen strange images when you close your eyes and rub them vigorously? This optical phenomenon, known as a phosphene, is characterised by the perception of lights despite the fact that there’s no light entering the eye when it’s being rubbed.
People who have gone an extended period without visual stimulus, such as prisoners placed in solitary confinement or campers stuck in a dense jungle at night can also experience this phenomenon. This is why it’s sometimes called the prisoner’s cinema.
The source of this entoptic phenomenon lies within the visual system itself. It is most often caused by some kind of stimulation to the retina, whether electrical, magnetic, or mechanical. In addition, any random discharge of an electrical signal within the eye can also cause phosphene.
The eye can perceive light when none is present in several ways. In order for one to see, light waves must stimulate a person’s retina. The brain then translates those light waves into an image. However, physical, magnetic, and electrical factors can also stimulate the retina. Most strange lights that people see are actually induced by physical stimulus.
When people close their eyes and rub them, they activate cells in the retina. The brain is then required to interpret the signals into a visual image. This is why people see waves of patterns and colours. However, since there are no light waves actually encountering the retina, the brain cannot create an image, such as a burger or a sports car. Therefore, one simply sees colours and spots!