DS's neuropsych said he reviewed the literature at one point and said that the research doesn't support it for the most part. It probably depends on whether a) that is really the child's problem and b) how the therapy is done. I would want to see solid data before investing in that (unless you are lucky and insurance pays).
One thing to ask for is a depth perception test. A regular eye doctor can do this. DS had strabismus as a result of a brain injury, where a nerve in his brain was paralyzed and his eyes were literally looking in two different directions and it was very obvious. He also had obvious double vision, if someone held up two fingers and asked how many fingers he saw, he would say four. I remember he was trying to grasp a balloon ribbon one day, and he kept grasping at air about 12 inches to the right of where the real balloon was. When kids have eyes that aren't aligned, they have no depth perception. So when he was given the depth perception tests at the eye doc, they would ask him to pick the picture that was popping out. It was obvious he was randomly guessing. As his strabismus gradually resolved, the depth perception tests got better and he could see the easier more obvious ones (but still struggled with the difficult ones). After about 8 months he could do the whole test effortlessly, and then I knew his strabismus must be resolved.
