Hey,
by "controlling through eyes", do you mean the position of the the eyes in a video? This could be achieved via face-recognition, have a look at opencv.

But if you want to track the point where the user is looking (gaze-tracking), this more complicated. You would need to track the position of the pupil in relation to the eye's position. Though it works, it is not very precise due to low camera resolution. (The pupil only moves several pixels when looking around the screen).

Theoretically, this seems to be possible, but I have doubts that it would be even remotely accurate with a web cam. You would have to find the eyes on the face and calculate 3D vectors based on where the eyes are looking. As benja pointed out, that step is probably the main problem. The resolution on a camera is probably not going to be accurate enough to give a good vectors.