I don't know about the problem with your vision, but I think if you have phlegm in your throat which you can't expel, it might be in the tosil area. If phlegm
comes from your lower respiratory system, you should be able to cough up
or expel it. Although you don't feel you have mucus flow down through your air way, it still does. If you feel something in back throat and can't expel it, phlegm might come from mucus from upper sinus or from back throat. If it's clear, it's not infected.