Are these glasses too dark for indoor use (to prevent migraines)?

Dear Christinewas: Thank you for your inquiry. No they are not to dark for indoor use, however, it is up to the individual. Also, we do have many customers that use the sunglasses for migraines. Thank you

Do they also protect against 100% uva/uvb rays?

Yes, they are excellent in that respect. I wish I could find another pair that fit. As I stated, they were too large for a woman's face/head. But, I love the product.

Do these have blue blocker lenses?

Dear Damon:Yes, these are the blue blocking lenses. Thank you.

How can I tell if these would fit a 12 year old boy?

these glasses would be a bit too big for a 12 year old. but they are well made. If you have never wore these sun glasses they really don't block the sunlight but they remove 99% of the glare. They actually make things a little brighter. I have eye problems and am very sensitive to glare and uv and these work great.