Seeing moving dots when looking into bright blue light such as the sky is known as what?

The blue field entoptic phenomenon is an entoptic phenomenon characterized by the appearance of tiny bright dots (nicknamed blue-sky sprites) moving quickly along squiggly lines in the visual field, especially when looking into bright blue light such as the sky. The dots are short-lived, visible for a second or less, and traveling short distances along seemingly random, curvy paths.

The dots appear in the central field of view, within 15 degrees from the fixation point. The left and right eye see different dots; someone looking with both eyes sees a mixture.

The phenomenon is also known as Scheerer's phenomenon after the German ophthalmologist Richard Scheerer, who first drew clinical attention to it in 1924.

The dots are white blood cells moving in the capillaries in front of the retina of the eye.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 larger than red blood cells, but much rarer 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.