This is very good so parents and children alike will not have to keep visiting the optician for grade adjustment of the child's glasses. However, I am concerned about kids playing with the very high grade that may cause bad effect on their eyes. I remember when I was young, I played with my father's glasses with high grades. I kept using it as I wonder why my vision gets blurry instead of clearer. Then my father said I have a good vision so using a wrong glass with wrong grade will make my vision bad. That I think is the caveat to this device if kids are left to adjust the grade on their own.