I have a theory that hes lying about being blind. No basis really, other than we know he does lie a lot, and he lied a fair bit in oxygen itself. Plus nardock did say that if he came back injured, their friend in the vault would know about it, and doesnt that seem like just the sort of trickery the doctor uses all the time?
Im probably totally wrong but im putting that out there so if it is the case I can come back here and say told you so.
I think it probably is the master in the vault, since theyre both clearly and enemy but also a "friend"'. The question though is which one?
Remember, john simm is returning this series as well...