We have no problems using electrons when targeting tissues <2 cm deep. We use internal tungsten eye shields with an aluminum backscatter cap which reduce transmission to <5% with electron beam energies up to 9 MeV. Shiu et al., PMID 8655385. Depending on the calibration of the machin...

If the eyelid is part of the target, I typically use electrons with internal eye shielding. If the eyelid is not part of the target, I typically use either intensity modulated photon or proton therapy.   Consideration also should be given to whether the infraorbital nerve is part of the targ...

I agree with Dr. @Christopher A. Barker. In addition, MR is helpful in evaluating and tracking the nerve.