There are a lot of things to be said for ordering glasses for your child online: they're generally less expensive for one, and some online retailers have a better selection of children's frames. There are also things to watch for and think about though, if you do decide to order online. Make sure that the lenses you buy are polycarbonate or Trivex for your children, not plastic or glass. This is a safety issue!! You can read more about children's lenses at A Child%u2019s Eyes. First and foremost, you will need to know your child's pupilary distance, Have a professional do this measurement. you can ask at your eye doctor's, or at an optical shop. You will also need to know some other sizes to figure out which frames will fit your child.The first number in the eyeglass size is the distance across one lens of the glasses.The second number in the eyeglass size is the distance across the bridge on the eyeglass frame %u2013 sometimes referred to as the DBL (distance between lenses).The third number in the eyeglass size is the length of the temple (arm piece) from the front of the eyeglass frame to the end of the temple, which goes behind the ear.It is likely that your child will need to replace their glasses before they outgrow the frames. They'll either break the frames during their day to day activities, or they'll scratch the lenses or have a prescription change.Many retailer shops offer free replacement of lenses if the prescription changes in the first couple months, and a discount for the rest of the year. Most online retailers do not offer that.