Any number of things depending on what's going on. If it happens by itself it would make sense to see an opthalomologist. If you have other physical concerns a neurologist. And if there are other psychiatric issues a psychiatrist. But you'd have to be more specific as to what other concerns you have or if it happens by itself.
I read floaters can look like black cobweb type particles but I'm not sure if that's what you're talking about when you refer to "black tracers". You'll have to describe what's going on a lot better than you did and it's better just to ask a specialist like ILADVOCATE said.
Yeah your very vague but to begin with go see an eye doc, get your vision checked out, floaters can be a sign of an underlining medical condtion like high blood pressure, diabetes and they do look like a black cobweb floating around in your vision, each floater though is normally only seen in one eye at a time, so if your seeing black shapes in your vision and your seeing it with both eyes then it may not be floaters. In that case go see ur GP.
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