Blinded

When a creature loses its vision it gains the Blinded Condition

• A blinded creature can’t see and automatically fails any ability check that requires sight.

• Attack rolls against the creature have advantage, and the creature’s attack rolls have disadvantage.

You can not apply the Blinded Condition to a creature that does not have naturally occurring vision
If this effect is caused by a caster a creature can make a constitution save equal or higher than the casters Save DC, if they fail they can not resist the effect till the spell ends

Type

Physiological