If you can hit an eye socket sized target reliably in practice you will have no trouble hitting a big target like the throat or solar plexus under stress. If you don't practice you will do good to hit the broad side of a human under stress.
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The only problem with the real world on the street is, theory and practice go out the window. Trying to hit that small target while he's swinging back with whatever blade he's tried to mug you with, while his buddy is stabbing you in the back or side, depending on which way your facing, is just going to get you killed in a real situation. You will be facing at least two of them.
Have any of you people ever lived in a big city and dealt with real seasoned street criminals before?
They've practiced this stuff even in jail. They're fast, desperate, and they ain't about to give you a chance to pull a knife.
This whole thread has been from never-never land.
You never stand and fight, but keep moving in retreat and slash at any arm or weapon holding hand that comes near you, but just keep moving back out of range. The lookout will be jumping into the fight, so keep moving to keep him in your view keep moving. It's going to take place so fast, you won't believe it. Keep to very gross motor movements, and run like hell when you get the chance, while yelling. They don't like attention. If you can retreat for a few seconds while yelling, and keep a retreat going, they will probably give it up, and go look for an easier mark. The predators like to make a fast kill and get out of there, not hang around in a street fight. But they will fight if they have to, like when some misguided keyboard commando pull s knife and tries to kill them. Rule of the street is, when somebody tries to kill you, you try to kill them right back. By engaging in a knife fight, you've given up the main advantage you had, that of being a mark that is escaping. While you try to stab him in the eye, where do you think his knife is going?
You're not Rambo or some idiot in a V for Vendetta mask. You're a citizen going about your business and just defending yourself. The whole idea is to make an opening to dis-engage, not take part in a knife fight. Maybe you haven't heard, the winner in a knife fight is the guy who only goes to the ER instead of the morgue. Or maybe goes to the morgue last.
Even if you get away with it, legally, go and kill somebody, even a low life street criminal with a record as long as your arm, who has done serious time, the civil lawsuit from his family will grind you down for years to come. They'll have relatives coming out of the woodwork giving testimony how "he was a good boy, he sang in the church choir when he was 12 years old" and other such nonsense. Even if you win the lawsuit, the legal defense will break you, and you'll need a second mortgage on your home to pay the lawyers.
Take out somebody with a nice clean stab through an eye and you don't have a single cut on you, see what happens. You ain't gonna be in Kansas anymore Toto. It doesn't matter how you feel about it, or what kind of values you have, this ain't the wild west, you''re not the hero, and some political aspiring assistant D.A. is going to make the start of his career with you. Thats a fact. Kill somebody in todays society, and you have trouble like you won't believe, even if you are in the right. If you have a retirement fund now, you won't when they get done with you. But nobody is going to feel bad about some punk with some cut motor tendons in his wrist or forearm, or some broken bones in his hand. In fact, he'll loose so much face they'll laugh him off the street. You don't have to kill someone to stop an assault. In fact, in todays world, it's the last thing you want to do.
Some of you have to put your adolescent day dreams aside and live in the real world.
This whole thread has been so low road, I'm surprised it lasted.
Carl.
And they are common in bujutsu, as opposed to sport systems. Every gyuaku-te waza, for instance, incorporates what is most commonly used as an eye strike. No ninja blinding power needed. 
