Is there a test the can do to tell if my son is completely blind?

My son is 3 months old and has coloboma and nystagmus. We know for sure he cannot see in the left eye, and know for sure he sees light in the right eye, but since his eyes move back and forth all the time and he never focuses on anything. I was wondering if maybe they had a test to see exactly how much he sees.

but is there a way to test to see if he sees ANYTHING is what i guess i'm trying to ask. I know a babies sight is not fully developed for years. But if my son is COMPLETELY blind, is there a test like watching his brainwaves while pictures are flashed in front of him to see if he reacts at all./?

My daughter has an optic nerve coloboma and strabismus in the left eye. It was diagnosed at 6 months. There's no test for a baby that young. In time, you'll be able to just tell how well he sees by the way he interacts with things. My daughter is now almost 3 and we've come to realize through trial and error that she has no peripheral vision in the left eye, but otherwise can see just fine. Hang in there. It seems scary and overwhelming now, but it gets better. You'll be able to test his vision when he's more able to communicate with you.

It's really difficult to answer this type of question particularly because his eyes are not fully developed yet. You won't know his full potential visual acuity until at least 8 months, and even then a babies vision continues to develop over the next few years.