Brief Answer:
Floater have many causes.

Detailed Answer:

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One of the most important cause of floaters is Old age- Eye floaters most commonly occur as a result of age-related changes in the vitreous.Over time, the vitreous partially liquefies — a process that causes it to pull away from the eyeball's interior surface. As the vitreous shrinks and sags, it clumps and gets stringy. Bits of this debris block some of the light passing through the eye, casting tiny shadows on your retina. Retinal tears can occur when a sagging vitreous tugs on the retina with enough force to tear it.Retinal tear may lead to retinal detachment.Retinal detachment separates the retinal cells from the layer of blood vessels that provides oxygen and nourishment.In long term if left untreated may cause loss of vision in affected eye.
Retinal imaging is a recent technological advancement in eyecare. It enables your optometrist to capture a digital image of the retina, blood vessels and optic nerve located at the back of your eyes.The sudden appearance of floaters and flashes and reduced vision is usually presenting symptom of retinal detachment.

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