This is my first attempt to model a human.  I am using Carrara 8 pro.  I don't have ZBrush or anything like that.  I've used symmetry and the extrude tool with some success.  Now that I have the basic form, I am adding details. I want to keep everything symmetric, but I also want to add spheres for the eyes.  The eyes in the pic are primitives just to see what it would look like (and the hair is Amy hair from DAZ).

If I already have a symmetric model in the modeling room, is there a way to use the  Construct, add Sphere tabs and still maintain symmetry for the eyes?