When viewers looked at the gateway after the shield was raised, they wore dark goggles to protect their eyesight. Major McAndrews was offered no eye protection when he entered the room with the gateway.
When General Slater gave Major McAndrews the goggles, he tells McAndrews not to look directly into the portal. But 30 seconds later, first the General, then the Major, take their goggles off and stare directly into the portal.