Straight from a PVS-7 Night Vision Goggle Manual

Here's some text straight from a PVS-7 Night Vision Goggle User's Manual:

EQUIPMENT CHARACTERISTICS, CAPABILITIES, AND FEATURES

WARNING - EQUIPMENT LIMITATIONS

To avoid physical and equipment damage when using the AN/PVS-7 goggle, carefully read and understand the following safety precautions.

1. The equipment requires some night light (moonlight, starlight, etc.,) to operate. The level of performance depends upon the level of light.
   
2. Night light is reduced by passing cloud cover, while operating under trees, in building shadows, etc.
   
3. The equipment is less effective viewing into shadows and other darkened areas.
   
4. The equipment is less effective through rain, fog, sleet, snow or smoke.
   
5. The equipment will not "see" through dense smoke.
   
6. Adjust vehicular speed to prevent overdriving the range of view when conditions of possible reducation or loss of vision exist.

CAUTION:

The AN/PVS-7 is a precision optical instrument and must be handled carefully at all times to prevent damage.

The AN/PVS-7 is a hand-held, headmounted or helmet mounted night vision system that enables walking, driving, weapons firing, short range surveillance, map reading, vehicle maintenance, and administering first aid in both moonlight and starlight. Each unit allows for vertical adjustment (by using head straps), fore-and-aft adjustment, objective lens focus, eyepiece focus, and eye span distance adjustment. The goggles are also equipped with an infrared light-emitting source and a low battery indicator. The goggles automatically shut off when disconnected from the headmount or helmet mount. There is also a high-light cutoff feature that shuts of power to the goggles when they are exposed to high levels of light for 70 (+/- 30) seconds.

I thought it was interesting that it included "vehicle maintenance, map reading, and administering first aid." These are applications for night vision equipment you don't hear about very much.

Night Vision Goggles vs. Binoculars: Addendum

An additional point to the post below, is whether the night vision system comes (as part of the purchase) with a head mount and/or helment mount. Binoculars are typically heavy, due to the dual optics, and head mounting and helmet mounting becomes too cumbersome. So, if the system comes with a head mount and/or helmet mount, then this will be an indication that the system is more inclined to be used as a goggle, rather than a binocular. An example would be the popular AN/PVS-15 Dual Tube Night Vision Binocular. It does not come with a head mount or a helmet mount, and therefore it falls under the binocular category. However, that is not say that someone could not headmount it and use it as a goggle. It will just be a heavy off over the face.