Correct!itachi is not testing anything dude itachi is being controlled by impure world Resurrection
I think the crows eye is a special type of MS and like what other people have said, it is a counter to all other Sharingan's. Maybe the power could be like when another Sharingan look's directly into this special MS, it deactivates iteself and reverts back to a normal eye.
OR
This UCHIHA BLOODED crow (hence the sharingan!) is just trained to pluck any Sharingan eye's it see's =p j/k