Floaters

Floaters are ghostly specks, dots, or lines that drift across your visual field. They’re most often visible in front of a smooth blue sky or a blank computer screen.

At left is a simulation from Wikipedia. You can’t look directly at floaters, because they exist at a fixed relationship to your direction of vision. As your eye moves to look at them, they dart away at the same speed.

Floaters are a normal experience for people with healthy eyes, but a lot of them can also be a sign of a retinal detachment or other medical problem. Normal floaters are caused by cell debris from the natural degeneration of the inside of the eye. Bits of protein material are suspended in the gel-like vitreous humour inside your eyeball and drift down like flakes in a snow globe.


10 fun facts about floaters:

1. There’s a different set of floaters for each eye, and you can see each separate set of floaters by covering one eye and then the other.
2. You get more floaters as you get older, but young people get them, too.
3. Young peoples’ floaters tend to look more like transparent worms, older folks' floaters tend to be more like dark specks.
4. Floaters eventually settle down to the bottom of the eyeball. During the day when you’re vertical, they settle at the bottom of the eyeball. During the night when you’re sleeping, they settle at the back. 
5. If you tilt your head just right, you can sometimes get them to drift to the center of vision. 
6. You don’t see the floaters, but rather the shadow they cast on your retina.
7. Floaters are not optical illusions, but are called entopic phenomena. 
8. In bright light, when the pupil is contracted, the shadows cast by floaters are sharper, so they’re easier to see.
9. The gel-like vitreous humor gets more watery as you age.
10. In French they’re called “mouches volantes,” which means “flying flies."

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Sources: Wikipedia

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