In the episode “Oxygen,” the Doctor is exposed to vacuum for an prolonged period and
suffers blindness as a result of this exposure.
The Doctor reassures Bill that this condition is temporary, and that, once he has access to the resources within his TARDIS, he can deal with it (even if he has to implant the organs of a lizard).
BILL: You’re blind.
DOCTOR: I am? Well, that explains the bruised shins.
(Bill hugs him.)
DOCTOR: Oh, don’t get all gooey on me. It’s temporary.
BILL: Really?
DOCTOR: Yeah. Once we get back to the Tardis.
BILL: The Tardis?
DOCTOR: I’ve got stuff in there that’ll cure anything. Failing that, I think I’ve got some spare eyes somewhere. They’re from a lizard, but I’m sure they’ll fit.
Doctor Who, “Oxygen”
Later, however, it is revealed that he is still blind, a condition which he believes will be permanent.
DOCTOR: Nardole, I can’t. I really can’t! I can’t look at anything ever again. I’m still blind.
Doctor Who, “Oxygen”
Why is this? The Doctor clearly wants to have visual capabilities. He has access to all the medical resources of time and space (possibly including those of Gallifrey). Admittedly, there may be some that are too dangerous to be worth the bother of accessing, but we’ve seen highly advanced medical facilities that he’s been to before (New, New York, for example).
In addition, we know that the Doctor does indeed carry highly advanced synthetic body parts around in his TARDIS.
TANYA: You got your leg back?
DOCTOR: I had some spares in the medical bay. The Lothan, giant centipedes, experts in prosthetic legs. You’ll get the hang of it. You just have to train it to act like your own leg.
Class, “For Tonight We Might Die”
How, with all these resources, is the Doctor incapable1 of dealing with his blindness?
1: Besides, apparently, borrowing barely a few minutes of vision at a potentially ruinous future cost.