I took Ds2 to get his eyes tested by a behavioural optometrist today. As he is only 4 there is a limit to what they can test and do but she confirmed that his actual vision is okay and also what I suspected - that his motor problems mean he has trouble with tracking and he tends to move his head instead of his eyes.
Anyway she suggested testing to see if he has any retained primitive reflexes. I can't find anything in the scientific literature about this although there is quite a lot on the web generally about how it can inhibit development further if they persist. So I wondered if anyone else has any experience or knowledge of this? Or knew of any evidence to suggest it is a useful thing to do.