[ An eye?? That's a much more invasive addition than a traditional prosthetic. He rises up on his toes to help the difference in their heights, leans uncomfortably close, and sets a thimble and forefinger to pull back the skin around the eye. No scarring. It looks natural. It shouldn't. ]

Hydra used ocular implants to force victims to act as agents against their free will. It's close to the brain, and anything I could build to replace it would require means inaccessible to us here. Look to your left?

[ he's mostly mumbling to himself. If the affected victims are somehow sleeper agents now, it wouldn't make a difference in the end anyway. ]