How would you manage a metastatic lesion abutting the optic structures (globe, optic nerve, etc)?  

Generally, if I'm treating a metastatic lesion abutting an OAR - in this case, it's an optic nerve - I try to keep my Dmax to the optic nerve/chiasm to 8 Gy (allow up to 10 Gy if needed). If I can't achieve those constraints, I would favor fractionated radiosurgery. There are some papers looking at ...