Most eye floaters are caused by age-related changes that occur as the jelly-like substance (vitreous) inside your eyes becomes more liquid. When this happens, microscopic fibers within the vitreous tend to clump together and can cast tiny shadows on your retina, which you may see as eye floaters..
Contact an eye specialist promptly if you notice:
Many more eye floaters than usual
A sudden onset of new floaters
Flashes of light
Darkness on the sides of your vision (peripheral vision loss)
These painless symptoms could be caused by a retinal tear, with or without a retinal detachment a sight-threatening condition that requires immediate attention...
Eye floaters may be caused by:
Age-related eye changes. Eye floaters most commonly occur as a result of age-related changes in the vitreous, the jelly-like substance that fills your eyeballs and helps maintain their round shape. Over time, the vitreous changes in consistency and partially liquefies a process that causes it to shrink and pull away from the interior surface of the eyeball. As the vitreous shrinks and sags, it clumps up and gets stringy. Bits of this debris block some of the light passing through the eye, casting tiny shadows on your retina.
Inflammation in the back of the eye. Posterior uveitis is inflammation in the layers of the uvea in the back of the eye. Posterior uveitis, which can cause eye floaters, may be caused by infection or inflammatory diseases, among other causes.
Bleeding in the eye. Vitreous hemorrhage is bleeding into the eye's jelly-like vitreous. Bleeding in the eye can have many causes, including injury and blood vessel problems.
Torn retina. Retinal tears can occur when a sagging vitreous tugs on the retina with enough force to tear it. A retinal tear may cause new floaters to appear in your vision. Without treatment, retinal tear may lead to retinal detachment an accumulation of fluid behind the retina that causes it to separate from the back of your eye. Untreated retinal detachment can cause permanactors that may increase your risk of floaters include:
Age over 50
Nearsightedness
Eye trauma
Complications from cataract surgery
Diabetic retinopathy
Inflammation in the eye ent vision loss...
http://www.mayoclinic.com/health/eye-floaters/DS01036