The creature cannot see. It takes a –2 penalty to Armor Class, loses its Dexterity bonus to AC (if any), and takes a –4 penalty on most Strength- and Dexterity-based skill checks and on opposed Perception skill checks. All checks and activities that rely on vision (such as reading and Perception checks based on sight) automatically fail. All opponents are considered to have total concealment (50% miss chance) against the blinded character. Blind creatures must make a DC 10 Acrobatics skill check to move faster than half speed. Creatures that fail this check fall prone. Characters who remain blinded for a long time grow accustomed to these drawbacks and can overcome some of them.
Marius, Scholai Armsmaster says: Since a Blinded creature loses its dexterity bonus to AC, it is vulnerable to sneak attacks and touch spells. Blinded is one of the most powerful options under the Dirty Trick combat maneuver. If you’re having trouble hurting your enemy or want to help your allies against a tough foe, a blind attempt can be an excellent use of your time. Blinding is particularly effective against spellcasters, who cannot cast target spells like Charm Person or Finger of Death if they cannot see their targets.