No. Floaters can hardly be detected by vision test because it only affect your vision slightly. However, floaters may be caused by retinal detachment or diabetic retinopathy. While flashes have something to do with retinal tears (breaks) or detachment. If you don't treat them , they may cause blindness.
No. In most cases, floaters and flashes won't cause damage to the vision. The floaters will get smaller and less noticeable over time and flashes will go away eventually. However, if they are caused by some problems, like retinal detachment or diabetic retinopathy, and you don't treat them as early as possible, they will cause total blindness.
Few people can get blind with flashes or floaters. Normal floaters are harmless and are caused by tiny specks of tissue inside the vitreous. When light comes to these specks, it creates shadows on the retina that appear to float moving around your visual field. There is no treatment for floaters and most people will ignore them as time goes by.
Most floaters or flashes are harmless to your eyes although they are annoying. They would not make you totally blind. But eye floaters in people above 45 years old require particular attention. Sudden forms of eye floaters in this population probably signify a torn retina, which needs immediate treatment from an ophthalmologist.