Sometimes, against a uniform, bright background such as a clear sky or a blank computer screen, you might see things floating across your field of vision.
This can be very irritating. What are these moving objects, and how are you seeing them?
These things that you see in front your eyes called “Muscae volitantes”, which is Latin for “flying flies”. They don’t come from outside, they exist inside in the eyeballs.
When you see them, they may act like live creatures, because they move and change their shape, but they are not alive.
“Flies” are actually tiny objects that cast a shadow on the retina, the light sensitive tissue, located in the back of the eye.
They can be a part of the tissue, red blood cells or clumps of protein and they move everytime you start moving your eyes.
Michael Mauser explains this visual phenomenon in the video below