'Cylindrical power' in medical terms is called 'Astigmatism' is a condition in which there is blurred vision
- due to irregular shape of the Cornea
- the surface of the Lens
The only treatment at this age is wearing prescribed glasses.
I know it is quite difficult as a parent to accept the fact and his regularity in using glasses. But you might be surprised to see that Children with such significant power will be happy using the glass as they can see things better.
All you must do is encourage him wearing it throughout the day and take him for a checkup once every 6 months or as suggested by your eye doctor.And get a Corneal Topography scan done to check any irregularities in Corneal shape [ and a Cornea specialist opinion if told by your doctor].
If it was my child I would get him glasses right away. I hope this helps.Take care.