Blindness is a condition affecting a player/NPC if their vision has been limited, causing them to see hardly anything at all. It usually happens in darkness, either at night or during dusk/dawn twilight, if staying in a wooded hex.
Blindness can also be caused permanently by destruction of the eyes in battle. This effect is displayed as "No Eyes" in the "Current Conditions" section of the "Items screen".
When a person becomes blind, their maximum action points will be reduced to one. If blind in combat, accuracy will be heavily impaired.
Staying in a hex with a source of light - campfire, torch, flashlight or just a artificial ambient light - will remove the condition and prevent it from be applied again, as long as the source stays valid. If it is removed for some reason - fire dying out or power in batteries running out - the Blind condition will be re-applied immediately.