Second Pair
I would recommend when you go back to hospital for a check up is to ask for another voucher for a second pair of glasses. I made the argument that while we were trying to establish him wearing glasses, if he broke them we would be back to square one while they were being mended.

Techniques for getting your child to wear glasses
I’m not sure if there is a perfect age at which your child has to start wearing glasses, but somehow I feel three years old isn’t the easiest! It took us six months to get our son to wear his glasses most of the time.  We had taken the eye hospital at its word when the doctor said – don’t worry too much to begin with, just encourage him to wear them. A few months later they began to get more insistent with us that he really needed to wear them to get the benefit of early diagnosis.  In the end, after trying out strategies that Supernanny would have been proud of, it came down to simple bribery! He was allowed to watch his favourite programme if he wore his glasses.  As soon as he took them off the television went off.  Once this had some success, we extended it to watching anything on television required him to wear his glasses.  What would then happen was that he’d go off and play, forgetting he was wearing his glasses.  We then built up getting him to wear his glasses for other activities with very little protest.  The last thing was getting him to wear them out of the house.  He still has days when he doesn’t want to wear them.  I try to remain firm, but avoid a big scene if he refused to put them on.  If he remains adamant that he’s not going to wear them, I put them away and try half an hour later.