Boy, can I feel for you, D.!
My son has worn glasses since he was 10 Months old! No Joke! He has something called Duanes Refractory Syndrome (DRS). This basically means one of his eyes will not turn outward, but inward only, and the vision in it is really bad.
Now, the biggest challenge you will run into is your child KEEPING the glasses on all the time, HIDING them because they don't want to wear them. I have found many pairs of glasses in the most un-imagineable places (think: Toilet, in the radiators, behind major appliances...LOL).
It will all be in the way you spin it to your child; Let HIM pick out the kind of glasses he wants and he'll be much more likely to wear them.
Another positive - you will get MORE attention from strangers who tell you how "ADORABLE" your child looks when he wears them.
Bottom line - thank God it's only glasses, and it's not something worse. Your biggest challenge will be having your son KEEP the glasses ON when he is supposed to! And now that my son is 5, and can tell the difference when he has them on and when he doesn't.
I understand how you feel, though because I went through the same thing. Please don't hesitate to email me directly if you have any questions: ____@____.com luck to you!