You can make them smaller but, as you pointed out, there are no leaves in the middle of the plant. You will have bare branches for a season before leaves grow. I have cut them to the ground and they grow back.
I can't tell from your photos if the boxwoods have another problems. Maybe some closer photos will help. How often do they get watered? How long since they have been sheared? Are you looking at the brown edges of leaves that have been cut in half?