What is the latest update on your sons condition?
Are you indicating that one Doctor determined the prescription before dilation and one after dilation?
Your son is 8-1/2 years old. Can we assume that you were present during both Doctor's exams? Some Doctor's have no patience for examining children. You should evaluate the overall demeanor of the Doctors examining your son and were they using identical equipment as far as you could tell.
The exam by the ophthamologist included dialeted pupils. An assistant performed a series of exams then they use some droplets that were going to dialate his pupils. After fifteen minutes he was called in for the eye exam. he was then given some shades to avoid the sunlight for a few hours. What is the difference in the eyes Rx If the second exam's Rx is a little stronger?
You should consider getting a third opinion from a pediatric ophthalmologist with a dilated cycloplegic refraction to see who is closer to exact. Both are similar but ophthalmologist's Rx is a little stronger.
HV