Floaters are a result of changes in the vitreous body, the colloidal gel that occupies most of the hollow sphere of the eye. Aside from maintaining good nutrition, taking anti-oxidant vitamins, and following a healthy lifestyle, Ophthalmologists have no specific answer on how to prevent them.

Normal eye anatomy
Schematic of eye with floaters
Asteroid bodies - often difficult, but not impossible to treat with laser.
The vitreous gel is 99% water and 1% solid elements. Of the solid portion, there are collagen filaments and hyaluronic acid molecules. The ability of hyaluronic acid molecules to retain water molecules is an important factor in maintaining the gel consistency of vitreous. With age, there is a depolymerisation of hyaluronic acid, causing these molecules to release their water and form lacunae i.e. pockets of liquefied vitreous. The collagen 'filaments' aggregate to form larger 'fibrils', causing further collapse of the vitreous gel structure. This process is known as vitreous degeneration and 'syneresis'. The collagen fibrils may 'float' within the liquid vitreous pockets, giving the patient a sensation of floaters.

The same process that causes floaters may cause flashes of light. When the vitreous pulls on the retina - to which it is attached - the photoreceptors are mechanically stimulated. The retinal cells are incapable of perceiving pain, pressure, or temperature. The only stimulus that the retina responds to is 'light'. So when the retinal photoreceptors experience mechanical stimulation because of the vitreous pull, they send a signal to the brain in the form of disorganized light, which is perceived by the brain as a 'flash'.

Well suspended mid-vitreous floater

Edge of collapsed vitreous bag
With the accumulation of enough lacunae (liquified vitreous pockets), the vitreous framework collapses and the vitreous completely separates from the retina. This process is called posterior vitreous detachment. Tissue may tear from an area adjacent to or from the optic nerve head due to an acute posterior vitreous detachment. This tissue (called Weiss ring) is usually visible as a large floater.
Posterior vitreous detachment occurs in less that 10% people under 50 years of age but in more than 60% people who are over 70 years of age. It is more common for people who are nearsighted, who have had an eye injury, have undergone eye surgery,or have had inflammation inside the eye.

Vitreous floaters

Floaters in Vitreous Syneresis (liquifaction)
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