The strabismus is usually treated surgically
If nothing is found, then it could be corrected with surgery, I'd think.
Make sure something else isn't going on in addition to the astigmatism.
Rarely something in the upper lid can induce an astigmatism, but could also make the eyes look different, so make sure you get it checked out!
Assuming no direct facial trauma, and just a closed head injury, if the double vision were horizontal and at distance, one would think about a 6th nerve palsy, possibly bilateral 6th (in which case the images would get further apart looking both right and left.) If the double were horizontal at near, convergence insufficiency would be high on the list (very common after concussions).
If it were vertical double vision, one would think about 4th nerve palsy or palsies.
If there were direct facial/periocular trauma you would also have to think about orbit fractures with globe displacement and/or muscle entrapment.
In all these cases, it should only be binocular diplopia, i.e. using both eyes together. Covering an eye should resolve the double vision. If the diplopia persists monocularly, then think about a dislocated lens or IOL and rarely a retinal detachement.
Floyd A. Warren, M.D.