As seen in the image, Sigma can remove one's eye. Once done, Sigma can do three things one; The basic function completely destroy the eye. Two, when he removes the opponents eye, he can take it link it with his very own, using it as a third eye. Or three, take the eye, using it for later means. Sigma has also stated, that if one is in Sage Mode he can use this technique instantly, by connecting his own.