This type of debuff means temporary blindness & causes significant accuracy losing. Temporary blindness inflicts on enemies when they affected by very bright light. Exactly it doesn't let ranged enemies get normal precision. Eg: Gun Puppy after its blinding'll shoot its bullets not directly on player because to shot angle'll added some random number (-45o - +45o). So its shot'll be not so dangerous - so blinding weapons're especially efficient against ranged enemies. Also blind doesn't let enemies to cast any type debuff to player (fire, shock etc.). It's useful too - because eg sometimes freezing Howlizers (or something else) bind me onto one place & then i become surrounded without getting one little chance to victory. Also blindness causes some enemies (same as Wolvers) randomly drop onto floor while moving, but not large chance. Last: it makes enemies vulnerable to level floor traps.

Each family of monsters're vulnerable to Blindness, except slimes - because they'ven't eyes.

These weapons can inflict Blindness:

Avenger & all its derived.
Prismatech & all its derived.
Sun Shards & all its derived.

These armor've resist to Blindness:

Mining hat - slight resist to Blindness.
Cyclops cap - slightly makes player more vulnerable to Blindness.
Divine & all its derived - good resist to Blindness.

Also healing units (Silkwings, Gremlin Menders) get weak elemental attack that damages by light & also may to blind player, but it's low using priority &'ll used only when enemy's alone.

Note: for blinded player Chromalisks in stealth mode're absolutely invisible.

Debuff symbol:

here