Dr. Cranford is doing a poor job. The balloon is too far away for Terri's short vision. He's moving it too fast as well -- brain-damaged patients react slowly. It's a wonder that she can keep up with him at all, yet she does track the balloon on both sides of her head, and over her head.
Even more remarkable since the autopsy proved she's been blind for years and all that, and anybody like Dr. Cranford who says otherwise is lying or incompetent.
The only problem with that video is that Michael's attorneys got the sound turned off in court. And our detractors claim fake! LOL