Most eye floaters decrease in size and darkness with time. Some of this is due to actual absorption of the floater through the natural processes within the eye. Eye floaters may also shift in position within the eye, resulting in less of a shadow effect. In addition, the human brain tends to adapt to and often become used to the presence of eye floaters, ignoring them in a manner similar to the way a person only notices the feeling of shoes on their feet when they think about it.
Eye floaters eventually tend to become less bothersome, both through reduction in density and size and the above described process of neuro-adaptation.