wanted to share my experience with VT. DS was diagnosed with convergence insufficiency when we were in the UK, I believe he was 3. Was not picked up here by an optometrist but when we went to see a pediatric opthal., she did she pick it up along with intermittent exotropia. DS never complained about headaches or seeing double or anything really, but at that age, he didn't express things like that much. In any case, he was about a year to 1.5 years ahead in reading for reading. What prompted us to seek vision therapy was the fact that yes, it was obvious he had the convergence issue (when focusing on a very close letter for example, coming to about an inch away from the bridge of his nose, he couldn't keep his left eye focused at close range, it would slide to the side after about 1 second of focusing). All his life he has had issues with catching balls, knowing where things were in his space..I mean we would say, it's right there to your left!! and he couldn't see it..But no problems with balance, riding bikes whatsoever.
Intense 4 months of therapy but almost all of it was at home, after meeting with doc every week. I'm not going to lie, it was tough. BUT, it has fixed his convergence issue. He can focus at close range very well now and his reading really took off after that.

This year we had a follow up appointment with another behavioral opt. (we moved), and he doesn't have the convergence issue, but still sees the exotropia. We never see it, but apparently it may not be visible to us. Another couple of thousands for therapy, so we called his first pediatric opthmal. and she doesn't recommend VT for this, stating that it really only helps with convergence which by the way she never recommended therapy for, just wait and watch.

We don't know if we should proceed or not. He does have struggles with homework sometimes and wonder if a)getting more VT would help and b)if it really works for exotropia.

On the reading note, your DS is obviously very gifted and my DD is HG but FWIW she didn't really read well and regularly until about 6 months ago. Preferred to be read to. But the rate in which she has progressed has been incredible. So in agreement with Polarbear, it is the rate in which she is tracking that is indicative of her abilities. And she sometimes gets very simple words wrong or substitutes but I believe it is due to her reading in her head so quickly and she's already processed some of the sentence before she spits it out (hope that makes sense). She can read much faster silently then out loud. Also when she first started to read regularly, she would often pause at or mistake the easy words and get words like "procrastination" for example. But she has now outgrown that.