Poor dog is probably blind now.
Just in case you ever need to know it, the barbs on porcupine quills are arranged in spirals around the shaft, just like screw-threads. Don’t yank the quills out. Rotate them with a pair of pliers and they will come out like a screw. This procedure is slower than yanking them out, but much less painful and damaging. About 90 percent of porcupines have quills that come out when rotated counterclockwise. If that doesn’t work, rotate the quills clockwise.