Foggles

Foggles are glasses that have been made to simulate foggy conditions to the wearer and are used in pilot training exercises. Foggles are frosted on the top half to limit the field of vision of pilots and force them to use only the flight instruments,[1][2] simulating the conditions of low ceiling of clouds, heavy fog, night, and other Instrument meteorological conditions (IMC).[3] Under these conditions, pilots must fly under instrument flight rules (IFR), rather than by outside visual references under visual flight rules (VFR).