Were characters able to see it on the show when he was getting extremely stressed, or was that something only viewers could see? I have a feeling that they probably had Bixby put contacts on to make his eyes for the effect, but there's one episodes in particular that comes to mind where the dude who was causing the character to get stressed should've had a good view of his eyes and thought it was strange and never found out about his unwanted ability to turn into the Hulk. It was the episode where he was in Las Vegas and he was getting roughed up by his boss.
God bless, Jason Scott Irelan