Floaters do not cause blindness, however the underying problem (why there are floaters) must be addressed. The most common cause is chronically elevated glucose levels, and that indeed may lead to blindness. You should get an evaluation for diabetes, to include an hba1c and glucose fasting test.
Floaters are very common, a lot of people have them and have no problems. Have you been to an Ophthalmologist yet to find out if this is indeed what's going on?