Washiken uchi (literally: “eagle-fist strike”) is referred to as a chicken-head strike within Goshin-Jutsu. Chicken-head strikes are an oddly-specific atemi, used to crush an opponent’s eyes; thus, chicken-head strikes are forbidden to use in kumite. Chicken-head strikes can be thrown from a variety of odd angles to the inside, outside, and straight-forward. Since it doesn’t take much strength to crush an eye, this is one of the few techniques than can be reliably called upon if your balance has been compromised.
To perform a chicken-head strike, bunch your fingers together, like an Italian-American stereotype. Then, pretend your hand is a bird's beak, which pecks your opponent’s eyes. Please note that this technique crushes eyes like they were grapes; it does not pluck them out of people's heads, like in Kill Bill.
[Photo of chicken head hand position.]
[Chicken heads fast and slow, from the front and side, inside, outside, and forward ]
This technique is reserved for advanced students -- not because it is difficult, but because up-and-coming karateka should be worry about more important things.