if this is similar to Parasitic Pandemic then Im all for it.I think the parasites are inspired by a real parasite that lives in the eyeballs of frogs.
Looks similar such that you can see them inside and the eye is swelled up.
She said she was checking the water quality for parasites and at the festival chapter, the guy with glasses commented something like "Ah, so some people are already developing antibodies!". I think this "researcher" is just finding it strange that these people who are native to this place are no longer "blind"~Water quality survey? So it is a mass town drugging/hypnosis thing?