Phosphenes can be caused by a variety of factors. Phosphenes occur when the individual perceives light when there is no light entering the eye. These include floaters, which are formations of protein clumps in the vitreous gel of the eyeball that can be seen when looking at a bright, blank background such as the sky Īnd Purkinje trees, which are images of the retinal blood vessels in one’s own eyes that can be seen when a light is shined into the periphery of the eye.Īnother type of entoptic imagery that you may be familiar with is known as a phosphene. Some of the most well understood entoptic effects originate within the eyeball itself. There are a variety of types of entoptic images which originate in different parts of the visual system. Therefore, for the purposes of this article, ‘entoptic’ indicates imagery that arises from anywhere within the visual system, from the eyes to the neural cortex. Given the Greek meaning of the word entoptic, I prefer the anthropological definition of the term. On the other hand, in most medical literature, entoptic imagery is defined as imagery which only originates from within the eye itself. This definition comes from the Greek translation of entoptic meaning “things perceived within vision”, and is commonly used by anthropologists and archaeologists (Williams & Dowson 1988). In their discussion of paleolithic cave imagery, Lewis-Williams and Dowson define entoptic imagery as visual experiences arising from anywhere within the optic system, which includes the eyes, the occipital lobe of the brain, and the many other portions of the neural cortex that process visual stimuli. Since it originates within the visual system, entoptic imagery can only be seen by the observer.įor clarity, I would like to include a quick note on the definition of entoptic imagery. The term ‘entoptic’ comes from the Greek for ‘within vision’, indicating that the images come from anywhere within the optic system, between the eye itself and the neural cortex where signals from the optic nerve are interpreted. Entoptic images are visual effects which originate within the visual processing system of the observer.
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