Heather, does he seem tired and/or agitated right after the sessions? Are you doing VT exercises at home, and does he seem more disregulated after those sessions? VT can definitely be hard work - my dd does not react in an increased sensory need but it's fairly obvious when she's had a session of VT that is tough - I imagine if she'd been through VT when she was younger it might have resulted in increased need for sensory input or stimulation.
I also wonder - did the psych who tested your ds do any other follow-up tests? Typically a neuropsych, when there is a similar split in scores between PSI and VCI/PRI, will administer a test of visual-motor processing that will help determine if the lower PSI (and potentially block design) scores are due to fine motor challenges or to visual challenges. My ds who has fine motor challenges had a similar dip in coding to your ds', but not symbol search - his symbol search was not as high as his other subtest scores but also not anywhere near as low as his coding. My dd who had severe double vision and has been through VT (successfully), hit the *floor* on symbol search - literally. One of her PRI subtests was also extremely low compared to the other two - I can't remember which for sure, but I think it was block design. For both of them, the follow-up Beery Visual Motor Integration test clarified the root of the problem (visual v motor).
Have you asked your ds how he feels about VT? Has it helped his vision at all yet? Does he like the exercises or do they bother him?
Also curious - are they doing any type of computer-screen or light therapy?
And one last thought - you mentioned your ds was better when he went on vacation from VT - were there other things left out of his schedule during that time? Are you sure it's VT, or could it be something else?
Best wishes,
polarbear
