You’ll have to drill down into L.Eye_Center in the outliner and make the meshes selectable. Then add them to the group. That gets them appended into your scene and once they’re in, you’ll have to make them non-selectable again.
But there’s a problem, still. When I did this, the pupil was ‘rolled back’ into the orb of the eye. I’ll leave that for you (or the next person) to sort out. 😉