Could be that you burned a bright image into either your cones or rods in your retina, rods are used to see "black and white" and cones are used for colors. You can burn them by look at the sun or other bright objects. You'll see the image In a black form when you stare at anything after burning it, also when you blink. Yet on the otherhand you could have roundworm parasites I'n your eye and they are eating portions of your eye thus you seeing Dots haha hopefully it's not that but it will be possible if you suddenly go blind.
These black spots you are seeing are called floaters. They come about when a portion of your retina detaches from the back of the eye. The blur is caused by debris in the vitreous that cast a shadow on the retina. It is not a serious condition. Read more on the condition here; http://www.aboutfloaters.com/black-spots-in-vision.htm.