Dead Space 3 Cheats
If you are using a PC with keyboard and mouse, WASD controls the left item, while the arrow keys control the right. Pressing WA or Up and Left goes diagonally that way, WD or Up and Right makes the icon move that way etc.
I found it very difficult to control the right icon with the mouse, so I tried the arrow keys as an alternative and it worked perfectly.
Second play through it was a lot easier.