You may sometimes see small specks or clouds moving in your field of vision. They are called floaters. You can often see them when looking at a plain background, like a blank wall or blue sky. Floaters are actually tiny clumps of gel or cells inside the vitreous, the clear jelly-like fluid that fills the inside of your eye. Although the floaters appear to be in front of the eye, they are actually floating in the vitreous fluid inside the eye. While these objects look like they are in front of your eye, they are actually floating inside. What you see are the shadows they cast on the retina, the nerve layer at the back of the eye that senses light and allows you to see. Floaters can have different shapes: little dots, circles, lines, clouds or cobwebs.
Floaters occur when the vitreous, a gel-like substance that fills about 80 percent of the eye and helps it maintain a round shape, slowly shrinks.
As the vitreous shrinks, it becomes somewhat stringy, and the strands can cast tiny shadows on the retina. These are floaters. In most cases, floaters are part of the natural aging process and simply an annoyance. They can be distracting at first, but eventually tend to "settle" at the bottom of the eye, becoming less bothersome. They usually settle below the line of sight and do not go away completely.
In many cases flashes and floaters are caused by age-related changes in the back of the eye. The age related changes are specifically related to changes in the vitreous fluid (gel material). The vitreous fluid gradually becomes more viscous or watery overtime. What happens after the age of 30 or so is that the vitreous might be watery enough to swallow clumps of material and is where the floaters can develop. These clumps of material floating inside the eye can cast shadows on the retina and is why people see floating spots.
Aside from maintaining good nutrition, taking anti-oxidant vitamins, and following a healthy lifestyle, Ophthalmologists have no specific answer on how to prevent them. Laser treatment has helped many people. It is a reasonable alternative to vitrectomy, an operation that is available if laser can't help.