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Encyclopedia > 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). These dots are due to the white blood cells that move in the capillaries in front of the retina of the eye, near the macula. The dots move somewhat in sync with the heart beat. Entoptic phenomena are visual effects whose source is within the eye itself. ... White blood cells (also called leukocytes or immune cells) are a component of blood. ... Capillaries are the smallest of a bodys blood vessels, measuring 5-10 μm. ... Human eye cross-sectional view. ... An eye is an organ that detects light. ... Human eye cross-sectional view. ...


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 don't absorb the blue light well, create gaps in the blood column, and these gaps appear as bright dots. The wavelength is the distance between repeating units of a wave pattern. ... To help compare different orders of magnitude this page lists lengths between 100 nm and 1 µm (10-7 and 10-6 m). ... Human red blood cells Red blood cells are the most common type of blood cell and are the vertebrate bodys principal means of delivering oxygen to body tissues via the blood. ...


In a technique known as blue field entoptoscopy, the effect is used to measure the blood flow in the retinal capillaries, which is important in diseases such as diabetes. The patient is alternatingly shown blue light and a computer generated picture of moving dots; by adjusting the speed and density of the computer generated 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. Diabetes mellitus is a medical disorder characterized by varying or persistent hyperglycemia (elevated blood sugar levels), especially after eating. ...


Scheerer's phenomenon should not be confused with "floaters" or muscae volitantes, which are larger and darker structures that usually move slower and along straight lines; they are due to debris floating in the vitreous humor of the eye. This article refers to the entoptic phenomenon. ... Vitreous humour is the clear gel that fills the eyeball, lying between the lens and the retina in the eye. ...


References

  • Scheerer R., Die entoptische Sichtbarkeit der Blutbewegungen im Auge und ihre klinische Bedeutung. Klinisches Monatsblatt Augenheilkunde 1924;73:67-107
  • Sinclair et al. "Investigation of the source of the blue field entoptic phenomenon." (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=2703307), Investigative Ophthalmology & Visual Science. April 1989;30(4):668-673

  Results from FactBites:
 
Blue field entoptic phenomenon (288 words)
In a technique known as blue field entoptoscopy, the effect is used to measure the blood flow in the retinal capillaries, which is important in diseases such as diabetes.
The patient is alternatingly shown blue light and a computer generated picture of moving dots; by adjusting the speed and density of the computer generated dots, the patient tries to match the computer generated picture as best as possible to the perceived entoptic dots.
Scheerer's phenomenon should not be confused with "floaters" or muscae volitantes, which are larger and darker structures that usually move slower and along straight lines; they are due to debris floating in the vitreous humor of the eye.
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