Ran across this just this past weekend. My son, who just turned 10, was once an amazing shot (started shooting when he was two). Within a reasonable range, he could hit pretty much whatever he wanted. Then he had a growing spurt, got braces, and glasses, and his shooting went downhill. I blamed it on his growing so much so fast, but now I think the glasses had more to do with it. I hadn't noticed, but he had changed his stance to accomodate for them. We had the opportunity to shoot with one of the best archers in the state last weekend, and he saw it right away. He went through the same thing when he got glasses, and said it really changed things for him. He helped my son figure some things out, and really improved his shooting within a few targets. One thing I noticed is he anchors with the string on the tip of his nose, head turned sideways. You may have to modify your anchor something like this to keep the string out of the way.

Chad