Inaccurate?

Hunter's Eye

(Player's Handbook II)

Divination
Level: Ranger 2,
Components: V, S,
Casting Time: 1 swift action
Range: Personal
Target: You
Duration: 1 round

Your vision blurs for a moment.
When it clears, you can see through your enemies' skin to spot their arteries, organs, and other vulnerable points.
Your slice into a foe with uncanny precision, allowing you to strike a foe's vulnerable points and deal extra damage.
This spell grants you the sneak attack ability.
You deal an extra 1d6 points of damage per three caster levels.
If you already have the sneak attack ability, this damage stacks with it.