Blue field entoptic phenomenon

Blue field entoptic phenomenon

The blue field entoptic phenomenon or Scheerer's phenomenon is the appearance of tiny bright dots moving quickly along squiggly lines in the visual field, especially when looking into blue light (such as the sky). [Scheerer R., "Die entoptische Sichtbarkeit der Blutbewegungen im Auge und ihre klinische Bedeutung." "Klinisches Monatsblatt Augenheilkunde" 1924;73:67-107 de icon] This is a normal effect that can be perceived by almost everybody. The dots are due to the white blood cells that move in the capillaries in front of the retina of the eye, near the macula. [Sinclair et al. " [http://www.iovs.org/cgi/reprint/30/4/668.pdf Investigation of the source of the blue field entoptic phenomenon] ." "Investigative Ophthalmology & Visual Science". April 1989;30(4):668-673. PMID 2703307]

Blue light (optimal wavelength: 430 nm) is well absorbed by the red blood cells that fill the capillaries. The brain "edits out" the dark lines that would result from this absorption. The white blood cells, which are much rarer than the red ones and do not absorb the blue light well, create gaps in the blood column, and these gaps appear as bright dots. They won't appear at the very center of the visual field, because there are no blood vessels in the fovea. The effect is rather weak, and many people don't notice it at all. It is strongest when looking at a smooth blue surface.

In a technique known as blue field entoptoscopy, the effect is used to measure the blood flow in the retinal capillaries. The patient is alternatingly shown blue light and a computer generated picture of moving dots; by adjusting the speed and density of these dots, the patient tries to match the computer generated picture as best as possible to the perceived entoptic dots. This then allows calculation of the blood flow in the capillaries. This test is important in diseases such as diabetes which can cause retinopathy.

Scheerer's phenomenon should not be confused with "floaters" ("muscae volitantes"). Scheerer's phenomenon is distinguished by the appearance of "multiple," "identical-looking" bright dots that follow each other "rapidly" along the "same path." Floaters are variable in appearance; although they sometimes are dots, they often have the appearance of threads or shreds of crumpled cellophane. Floaters remain almost stationary or drift slowly and do not follow well-defined paths. They are due to debris floating in the vitreous humor of the eye. There are also several phosphenes that need to be distinguished from Scheerer's phenomenon.

The singer/songwriter Juliana Hatfield alludes to blue field entoptic phenomenon in her song "I See You" which includes the line, "What are all those dizzy circles in the corner of my eye? / They laugh and float away as I look into the sky."

References


Wikimedia Foundation. 2010.

Игры ⚽ Нужна курсовая?

Look at other dictionaries:

  • blue-field entoptic phenomenon —    Also known as Scheerer s phenomenon, after the German ophthalmologist Richard Scheerer. Both terms refer to an * entoptic phenomenon characterized by tiny bright dots moving quickly and semi randomly across the visual field, especially when… …   Dictionary of Hallucinations

  • Entoptic phenomenon — This is a medical definition of entoptic phenomena. For an alternative use within archaeology please see Entoptic phenomena (archaeology) Entoptic phenomena are visual effects whose source is within the eye itself. (Occasionally, these are called …   Wikipedia

  • entoptic phenomenon —    Also known as entoptic imagery, entoptic image, and entoptic form. All four terms are indebted to the Greek words entos (inside) and opsis (seeing). Traditionally the expression entoptic phenomenon is used to denote any member of a group of… …   Dictionary of Hallucinations

  • Blue Arc Phenomenon — Das Blue Arc Phenomenon ist ein entoptischer retinaler Effekt, der auftritt, wenn man in Dunkelheit einen einzelnen Lichtreiz betrachtet – zum Beispiel eine rote Leuchtdiode in ansonsten dunkler Umgebung. Bewegt man die Augen leicht neben dem… …   Deutsch Wikipedia

  • Scheerer's phenomenon —    see blue field entoptic phenomenon …   Dictionary of Hallucinations

  • Floater — For other uses, see Floater (disambiguation). Floater Classification and external resources Simulated image of floaters against a blue sky ICD 10 H …   Wikipedia

  • Closed-eye hallucination — Closed eye hallucinations and closed eye visualizations (CEV) are a distinct class of hallucination. These types of hallucinations generally only occur when one s eyes are closed or when one is in a darkened room. They are a form of phosphene.… …   Wikipedia

  • Visual snow — is a transitory or persisting visual symptom where people see snow or television like static in parts or the whole of their visual fields, especially against dark backgrounds. It is much like camera noise in low light conditions. The severity or… …   Wikipedia

  • Phenomene entoptique — Phénomène entoptique Les phénomènes entoptiques sont des effets visuels dont la source est dans l’œil lui même. Sommaire 1 Définition et histoire 2 Exemples de phénomènes entoptiques 2.1 Phénomène pseudo entoptique …   Wikipédia en Français

  • Phénomène entoptique — Les phénomènes entoptiques sont des effets visuels dont la source est dans l’œil lui même. Sommaire 1 Définition et histoire 2 Exemples de phénomènes entoptiques 2.1 Phénomène pseudo entoptique …   Wikipédia en Français

Share the article and excerpts

Direct link
… Do a right-click on the link above
and select “Copy Link”