Floaters can appear and remain noticeable for long periods of time. This usually occurs as the vitreous (the jelly that fills the eye) becomes degenerated. This is usually a harmless process, although the floaters can be somewhat disturbing to the vision.
Rarely, as the vitreous degenerates, it can create a retinal tear (the retina is the back of the eye). Retinal tears can lead to retinal detachments, which can threaten the vision.
It is important to know the symptoms of a retinal detachment so that you may visit an ophthalmologist if they occur.
1. Photopsias - these are flashes of light in the peripheral vision that occur as the vitreous exerts traction on the retina prior to a retinal tear.
2. Increased amount of floaters - if the number of floaters increases dramatically. For example, suddenly going from 1 floater to 20 floaters.
3. If a sensation of a curtain falling over the eyes occurs (blurrying of vision).
I would like to emphasize that retinal detachments are rare while floaters and even photopsias are pretty common. I just think it is important that you visit an eye doctor immediately if any of the above occur.
I hope this is helpful...