Did you know?
For those who’ve never experienced this phenomenon, eye floaters are little oddly shaped objects that appear in your vision, often when one looks at bright light such as a blue sky. Their shapes vary greatly, but will often appear as spots, cobwebs, or randomly shaped stringy objects.
These are not optical illusions, but rather something your eyes are actually perceiving. There are a few different things that can cause this, but in most cases these eye floaters are caused by pieces of the gel-like vitreous breaking off from the back portion of your eye and then floating about in your eye ball.
more explanation : http://www.todayifoundout.com/index.php/2010/06/what-causes-eye-floaters/