"In his pursuit of federal legislation to "save" Terri Schiavo, Senator Bill Frist used his medical credentials to make his public diagnosis that Ms. Schiavo was conscious and aware. He based his medical conclusions upon that video tape of Ms. Schiavo supposedly showing her eyes tracking a balloon. Of course, the problem here is that Terri Schiavo was blind and physically incapapable of sight."

Such certainty. There are degrees of blindness. A blind person who can detect a balloon at around 3 feet is still blind. But if a person who is blind, is given a test which depends upon seeing clearly, such as "how many fingers I'm holding up", as to way prove consciousness, the person may not see the two fingers [or the hand] but it doesn't answer question whether the person can count.
Using a balloon just shows that Frist has a clue of what the problems could be. Vision, hearing, and other perceptions are complicated mental processes.