Just a few more details. The first time it happened we were on our way back from the Doctor because he had become not dizzy but he could not get his balance and couldn't stay on his feet. It passed but we went ahead and brought him in. The balance hasn't happened since, This was about 4 mo. ago. Since then he has had half his Thyroid removed because of a one inch tumor that was on it which was questionable. Today he could see only half of what he was reading on the computer and looking at the TV he knew that there were 3 people on the screen but he could see only one. And no matter which eye he put his hand over his sight remained the same. It lasted about 10-15 min.