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Floaters, or muscae volantes, are entoptic phenomena , or shadow-like shapes which appear singly or together with several others in one's field of vision. They can take the form of spots, threads, or fragments of cobwebs, that float before one's eye in the direction of the eye's movement but much more slowly.
Floaters are not uncommon, although they rarely cause problems for those who have them. Floaters can be a nuisance and a distraction to those who suffer from severe cases, as the spots seem to drift through the field of vision. Ophthalmologists believe that the shapes may be shadows projected onto the retina by tiny structures of protein discarded over the years and trapped in the vitreous humour in association with the ageing of the eye. It is not, however, only elderly people who suffer from floaters; they can certainly become a problem to younger people, especially if they are shortsighted. In some cases, floaters are congenital.
If flashes do occur, however, or sudden "clouds" of minute spots move across the field of vision (as a whole), they must be investigated immediately as they may be symptoms of retinal tear s or even a detached retina.
The cause of floaters is not understood. Some have associated their onset with mercury toxicity and liver function, among other things.
Normally, there is no treatment indicated. Vitrectomy operations to remove them are normally advised against as they are risky and may cause more severe problems or even blindness. One should bear in mind also that floaters become less annoying as the sufferer becomes accustomed to them, and may even disappear over time.