If you equip an ENVG-II in combination with the Special Purpose Suit and use either the night vision or FLIR mode it blocks your vision in the first person perspective.
The normal NVGs (Compact NVGs and NV Goggles) come down in third person and there is nothing on your screen in first person, but the ENVG-II comes down in third person but it also comes down in first person and is blocking your entire screen.