Does surgery help with strabismus for a nine year old? How successful was it ?

My nine year old will see the surgeon in three months at CHOP for an evaluation. Her regular ophthalmologist recommended the surgery now that she is nine. Shes been seeing him since she was about five. I always thought that maybe it would be best for her to just have the surgery at a very young age but she was seen by two ophthalmologists at two different well known ophthalmology hospitals and it was just recommended now at nine. How successful is surgery for strabismus?