Self Adjusting Spectacles (Beta)

I bet someone's already thought of this before but anyway this has been on my mind for many days now as I've seen people suffering from this problem of broken spectacles.

How about if we can have spectacles which can adjust themselves according to the person who's wearing them.It should not be very complicated (very easy to say that).The basic technique could be that we could have a device fitted into the spectacles which can detect the focal length of the eye when a person is wearing it and then it can create sort of a mirage or alter the focal length of the eye so the person can see clearly.That solves two problems.One,you don't have to worry about getting new spectacles every time your number changes cause it can self adust and your eyes don't hurt plus you don't have to spend hours trying to get the correct number.Secondly,if you happen to break or lose your spectacles,you can borrow it from someone who can do without them for sometime cause it can automatically adjust to your eyes.

Also,we already have photocromatic glasses(which darken up when exposed to sunlight).So if we can have them to self adjust too,then your spectacles can serve as your sunglasses plus you won't have any trouble driving or seeing with them on.Presently we dont have spectacles which can get cool blue or green colours in sunlight but I bet soon,we can use cobalt and iron possibly to get the glasses to turn to blue or green in the sunlight.It's not gonna be long before we can have all purpose self adjusting spectacles.
So scientists and developers,start working on me idea.

And yea,if nobody's thought of this before,I'd rather copyright it :D