Elle, Your neurologist is wrong. MG causes weakness, however, it also causes the secondary symptom of pain.
Anyone who has ever been an athlete of any kind, even dancing, knows that overuse of muscles can cause cramping, spasms, and pain. Duh.
With MG, that just happens sooner.
And eyestrain can cause pain in anyone, but it might happen sooner in MG, too.
The weaker the muscle, the sooner you have pain.
I suppose your neuro thinks that MS only causes pain, and not weakness?
Don't assume that pain is MG, because other things can cause pain, too.
JJ, Have your eyes been checked for neuritis?
Annie