1)
What is the significance of "le'Einei Kol ha'Am"?
1.
Rashi: It teaches us that there was not a blind person among them.
1
2.
Ramban: It teaches us that every single person witnessed how Hashem descended on Har Sinai in an apparition of fire.
2
1
Because following their acceptance of the Torah, they were all cured.
2
Since the Torah writes in Sh'mos (33:20) "Lo Yir'ani ha'Adam va'Chai" (Ramban).