'to turn a blind eye at/to sth'?

[Mehrgan]

Hi all,
Would anyone please tell me what preposition is used in the expression? Since we look 'at' things, I used to use 'at' in the expression up to yesterday a friend mentioned it had to be 'to'. I'd appreciate it if somebody told me if there's any special reason. Thanks a lot.

[emsr2d2]

Yes, we "turn a blind eye to something".