What is the worst case for NVG vision?

In the context of visual acuity, the worst-case scenario for night vision goggles (NVGs) relates to the ability of the user to see detail clearly. Visual acuity is typically expressed as a fraction, with the numerator representing the distance at which a test subject can see an object, while the denominator indicates the distance at which a person with normal vision can see the same object.

In this sense, a visual acuity value of 20/100 signifies that a person can only see at 20 feet what someone with normal vision can see at 100 feet, indicating a significant reduction in visual clarity and detail perception. While 20/70 and other values are worse than 20/30, they still represent better vision than 20/100, making 20/100 the worst performance in terms of visual clarity among the options given.

This reduced level of visual acuity can severely impair one’s ability to effectively use night vision devices, which rely on a certain clarity of vision to properly interpret the environment in low-light conditions. In practical application, this means that a user assessed at 20/100 would struggle to accurately interpret what they're observing through the NVGs, diminishing their effectiveness for operational use.