You should not prune these arborvitae any further. Arborvitae and other evergreens develop what is called a "dead zone" on the interior of the plant where there are no points of active growth. Fortunately, it looks like the deer did not eat completely into the dead zone or your plant, so they should continue to recover since it looks as if you still have some growing points left on the lower portion of the plants. You could lightly shear the top portion of the plant to even things out, but if it were me, I would leave them alone. Even light pruning may stress the plants further.

https://www.johnson.k-state.edu/lawn-garden/agent-articles/trees-shrubs/how-to-prune-evergreens.html#:~:text=Pruning%20junipers%2C%20arborvitae%20and%20yews&text=The%20dead%20zone%20is%20the,leave%20holes%20showing%20dead%20wood.

Once deer establish a feeding pattern in an area, it becomes very hard to break them of that behavior, so if this is the first season you are seeing damage, I recommend taking action to deter their browsing.

I strongly recommend putting up barrier fencing to protect them from further deer browsing. This is most important during winter, but if deer are hungry enough they will feed year round. Sturdy plastic or wire netting or burlap attached to stakes going all the way around the plants is best. Don't position it so close that it's going to impede air flow and/or sun exposure. Here's more information on deterring deer:

https://www.canr.msu.edu/videos/smart-gardening-to-deter-deer-1

https://www.canr.msu.edu/resources/smart_gardening_to_deter_deer