you are either experiencing vitreous flashes or starting to get a retinal detachment. If it's way out at the edge of your vision and a vertically oriented line, it's probably a vitreous detachment or vitreous tugging, if it's more central and more persistent, then it could be a detachment and you need to get it checked soon cause it can get bigger at anytime, especially if it's patchy and changing. Either way you should check with your eye care professional and have it checked, to be on the safe side.