Can multiple ear piercings affect vision?

Unlikely. The two should not be related. The external ear develops from tissue that is unrelated to the eye or optic tracts. Vision can occasionally be altered due to an individual's response to toxins, and theoretically, a response to the metals in the earrings could have an effect. Allergy patch testing to nickle and the metals used in the jewelry should rule this out.
No. Ear peircings in no way affect your vision. If you are haing vision problems after piercings... They are not related.
Not usually. Unless the eyebrow or eye lid is pierced i can't imagine there would be a problem. If structures directly around the eye are pierced infections there could cause risk to vision.