I'm pretty sure the remark about shooting at the tear duct was meant to imply that if you aim there, you're likely to get a bullet into the eye socket. FBI Sniper school taught us to aim for the bridge of the nose at long range with a hi-powered rifle, i.e. a .223 or 22-250. If you hit the nose, the bullet punches straight into the brain, if you miss by an inch or two the bullet will generally deflect into the eye socket, same result. Unless you're using a .308, shooting at the forehead is not a good idea, bullets tend to skid off the skull unless the hit is perpendicular to the bone. And when dealing with small caliber pistols, my best shot would be the eye sockets, or under the chin, ranging up into the brain. The problem is, in most close encounters, if your opponent realizes you're about to shoot, he'll drop his chin and/or duck his head. Then it's time to put as many shots into the chest as you can, fast. Then run like hell, while he's assessing the damage!
Papajohn