Specifically, the "grace" given those who've never heard of Christ is the "law of God/conscience" as stated in Romans.
If they reject it, they will perish. To gain eternal life through it, they must "do" it without violation. They will earn a "righteousness" that is by law.
Abraham, however, "believed God" and that was credited to him as righteousness. He wasn't very successful at keeping that law in his heart.
Exactly those who because of their age or incapacity have no concept of the "law of God/conscience", are truly blind. If you are capable of coming to the conclusion that "I see" then you are not truly blind. Indeed a truly blind man, a man blind from birth, has no idea of what it means to see. If he is then given even a molecule of light, then he can know what it means to see and he can recognize that he is walking in darkness. He can then choose to remain blind and continue to walk in darkness or he can choose to follow the light.
Jesus is the light to the whole world. That means you. That means me.