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Blue field entoptic phenomenon - Wikipedia
The dots are white blood cells moving in the capillaries in front of the retina of the eye.[5] Blue light (optimal wavelength: 430 nm) is absorbed by the red blood cells that fill the capillaries. The eye and brain "edit out" the shadow lines of the capillaries, partially by dark adaptation of the photoreceptors lying beneath the capillaries. The white blood cells, which are much rarer than the red ones and do not absorb blue light, create gaps in the blood column, and these gaps appear as bright dots. The gaps are elongated because a spherical white blood cell is too wide for the capillary. Red blood cells pile up behind the white blood cell, showing up like a dark tail.[6] This behavior of the blood cells in the capillaries of the retina has been directly observed in human subjects by adaptive optics scanning laser ophthalmoscopy, a real time imaging technique for examining retinal blood flow.[7] The dots will not appear at the very centre of the visual field, because there are no blood vessels in the foveal avascular zone.
eyes  visual  vision  eye  hn  blue  background  white  dots 
20 days ago by hellsten
How the Galaxy Note 7 iris scanner works
The Samsung Galaxy Note 7 has an iris scanner that keeps the phone safe from prying eyes. How does it work, however? Is it reliable and is it safe? We'll try to answer these questions for you...
smartphone  biometrics  security  samsung  eye  health 
26 days ago by orlin

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