You should not often wash your hair after the cataract surgery because the water may contain the bacterium which may infect your eyes. You could wash it on the backwards to avoid the water flow into the eyes. Or you could use something to cover on the eyes to avoid the water.
Though there are many taboos you should avoid after cataract surgery such as No TV, No computer and No reading etc, you can wash your hair as well as take a shower after the the surgery. But to not affect your eyes, you'd better have someone to wash your hair by lying back. Besides, you also need to wear some good shield that to protect your eyes while you wash hair. And if you take shower, you shall also protect your eyes and don't let soap and shampoos get into your eyes.
Well, generally speaking, it is dangerous to wash your hair. As we know that it can improve your vision permanently, while there are also many things you should pay attention to it. Well, you can wash your hair, unless you can make sure your eyes can not be moistened by the water. As we know that after the surgery, your eyes will be very sensitive and fragile. So if you let the water in your eyes, your eyes will be infected easily by the viruses. So just be careful about it. Also, you should pay attention to other things. For example, you should avoid eye injuries by wearing a protective shield at night and with naps until you are advised by your doctor. Also, you should remember not sleep on the side of the operated eye for the first night.
It is safe to wash your hair four or five days after the cataract surgery. For the eyes are likely to become inflamed and irritated, you should be careful not to splash water or shampoo into your eyes. If you feel four or five days are too long and you really can't bear such a long time, you can ask others for help or wash your hair at the Barber's. It will be completely safe to wash hair as usual after three months.