I used to get a lot of little black dots and 'bubbles' when I was working and went to a specialist about it only to be told "Everybody has them."
Some are more noticeable than others, some are transparent, but we all have them to some extent. They're just 'debris' in the bloodstream that happen to be passing through the sight area apparently. If they are 'permanent' then more is going on, or it's just 'stuck', but if they're only around occasionally then up with them we have to put. Mine went away to unnoticeable when I stopped working, and stressing but still get the odd black one, usually just a 'bubble' one though.