Eye prescriptions, is there a scale?

I am uming you are a young person if you can still see quite well without your gles. There really is no scale at this point for you. When someone is far-sighted, such as yourself, and he/she is young, he/she can focus the eye to see more clearly (called accommodation). The older you get, the less able you are to do this. Therefore, the scale is a dynamic one, meaning it changes from person to person with respect to his/her ability to accommodate. The story is completely different for near-sighted people. Their scale is a little easier to predict, but becomes less reliable at higher prescriptions.