Hi Pemberley,
My dd13 was diagnosed by a DO with vision challenges when she was 8 years old (2nd grade). Like your dd, her diagnosis was a complete surprise to us, and came after a recommendation from neuropsych testing.
Double vision she can force together but it doesn't come naturally. Her eyes each see a different image so her brain has been alternately turning off one or the other.
Our dd had severe double vision and like your dd, one eye was shutting off when it was too much for her brain to deal with. In our dd's case, it was the same eye that shut down each time, so we were able to look for clues re when the eye was shut down - dd would tilt her head when reading or looking at things. She also had a habit of putting her head on the table and looking sideways when she did her homework.
She has been compensating, compensating, compensating her whole life.
This explains why she *has* to hyper-focus on tasks and probably has led to many of her processing issues.
Just a matter of semantics here, but if your dd truly has processing issues, the vision challenge isn't really causing them. What might be happening though is that what looks like a processing issue might really be a vision challenge, and once she's had the vision issue remediated, what looked like a processing issue might disappear.
One thing about my dd - she struggled tremendously to learn to read, but after only a few months of vision therapy (at 8) her ability to read just suddenly turned on and she was reading like gangbusters. Since that time it's been a battle to get her nose *out* of a book

Also likely contributing to her headaches.
Absolutely!
We will be driving to "vision gym" 45 minutes from school/ 30 minutes from home 1-2 times a week for the next year.
Our dd did vision therapy for a little over a year, once per week at the DO's office and 2 times daily at home. It was a lot of work (plus we had an equally long drive), but it was well worth the time invested. I don't want to scare you with the next part of our story but I also think it's something to be aware of. The improvements didn't last forever. DD's vision never went back to as much of an issue as it was before VT, but about 2 years after she'd quit she started having double vision again and went back for another 8-9 months of VT which once again cleared it up. That's now been a few years ago and she tells me now that she does have to work at keeping her eyes focused together, but she doesn't feel like she needs any more VT. She's doing really well in school, and she's a very mature 13, so I trust her in making that decision for herself.
I'm hoping the exercises can be done in school as we have found that DD puts in 100% effort in school all day no matter how difficult as long as she doesn't have to do more after school.
My dd didn't do the exercises at school, but we did take her out of school for VT. Part of the reason for that was that we've got 3 total kids all with busy after-school activities, and VT was so far away it would have created a huge challenge in terms of our family life. The second reason was, though, that VT was hard work, and I felt like it shouldn't be a huge add-on to school which was already a day full of hard work. The exercises we did 2 times per day didn't take that much time - 20 minutes each, and it was easy to fit them in as part of our morning and evening routines.
DD did do some VT things during the school day as needed to help keep her eyes focused. She has tricks - things like drinking from a straw, doing pencil pushups etc - that helped when her eyes had trouble tracking. I am not sure what she did to help with her eye shutting off, but can ask her later.
She compartmentalizes and school is work time as long as outside of school she can let it all go and relax, focusing on things that are easier and enjoyable.
FWIW, the actual VT exercises aren't all that horrible, although they can be a bit of a drudge. Some of them are a little fun. Our VT also integrated things like bal-a-visx (I think that's what it's called, can't remember for sure) and Brain Gym, and dd liked those. All my kids liked bal-a-visx
I suspect you'd have a tough time integrating the actual exercises (full suite) during the school day because it requires 20+ minutes of one-on-one time from a staff member.
District, who has basically been agreeing to any and all requests we have made as a way of compensating for how terribly DD had been treated early on, is saying vision therapy is not scientifically proven and they usually don't support these services.
There are a lot of people who believe this. You noted that the first eye dr you took your dd too didn't believe it. I think that if you want to argue convincingly to your school staff you'll first need to let them know up front that yes, there are people who claim it "cures" a whole host of things such as ADHD, LD, etc, and that's not what it is. It's a method of strengthening weakness in the eye muscles - because that's really what it is. The double vision your dd has *isn't* dyslexia etc - it's a muscle weakness, and it impacts her ability to fully participate in her FAPE.
Next thing - you have the DO's report, and you have a recommendation for DO testing through the last round of testing your dd went through. Those are professional reports which clearly have belief that it will be of benefit for your dd.
I'd ask the DO if he has any scientific research he can point you to that you can use to show it works.
Does the developmental opto's explanation make sense to those of you who have been through this? Any questions I should be asking?
Yes. Totally makes sense. I would go to her VT appointments with her and watch what they do with her. That was really helpful for me in understanding how to help our dd at home. I would also pick up a ton of clues while watching where the VTherapists would say - see how she's bending her head, that means she's shut down that one eye... etc.
I plan to argue both the compartmentalizing and the fact the this was a recommendation from the psychoeducational eval (which the district paid for...). Any other arguments I can make to have the 15 minutes 3-4x a week included in her IEP?
Have you tried asking the DO for suggestions? It's possible they've had other patients ask for services through the schools. DD had a friend who was receiving VT through our DO at the same time DD first went through it and she was able to get the services through her IEP. That's been years ago now and we've totally lost touch so I have no idea how they actually convinced the school district to include the VT.
Another thing you might try is talking to your dd's OT (if she has one at school) - some of the things they do as VT exercises are remotely similar to OT exercises... I'm reaching here lol!
My last question - why only 3-4 times per week? Just curious. Our DO was much more aggressive about the importance of daily practice.
Best wishes,
polarbear