Blocks lighting up when breaking them, graphical glitch.

Pretty straightforward, whenever I try to break a block, the breaking animation lights up the entire block, as shown in the screenshots below.

Tested this on various blocks. The brightening also seems to flicker and tear when moving while breaking due to a changing view-angle.

I don't know if this is intended, but it's pretty annoying :\
I'm using a Sapphire Radeon HD6870, with the latest Catalyst drivers.

EDIT: sorry, seems to be an Optifine issue, mark as resolved please