If someone has eyes in the back of their head, they are very observant and notice everything happening around them. You need eyes in the back of your head to look after young children.
before your very eyes
If someone does something before your very eyes, they do it in front of you, without attempting to hide what they are doing. Before my very eyes, he took the rubbish and threw it into the neighbour's garden!
cry one's eyes out
If you cry your eyes out, you cry a lot and for a long time. My son cried his eyes out when he discovered his bike had been stolen.
eyes like a hawk
If you've got eyes like a hawk, you have good eyesight and notice every detail. Of course Dad will notice the scratch on his car - he's got eyes like a hawk.
keep eyes peeled
To keep one's eyes peeled means to watch out very carefully for something. I mislaid my wedding ring at home, so I asked my children to keep their eyes peeled.
with one's eyes open
If you do something with your eyes open, you are fully aware of what you are doing. I took on the job with my eyes wide open so I'm not complaining.
eyes on stalks
If your eyes are on stalks when you look at something, they are wide open with surprise or amazement. The child's eyes were on stalks as he watch the magician's performance.