-50 & +50? Surely that's -0.50 and +0.50. My eyes are -0.75 which means I'm slightly short sighted. I can function without glasses, but driving is a bit of a nightmare! Sign posts are not easily visible, which can cause obvious problems.
If it's -5.0 and +5.0 then that means your totally blind and might as well have your eyes closed:d glasses are a must! It's amazing you've managed to get around if that's the case.
I'm no professional but with having a + & - prescription you'd need glasses? That must confuse your eyes and could explain your headaches! When I had my eyes tested a few years ago they told me I had -0.75 and that it was my choice if I wanted glasses or not because it's not a strong prescription. Sounds like yours is 0.50 which is not strong at all. I opted to have contacts and now i can't live without them.
My advice, go see another Optician, but at ALL costs avoid Specsavers, they have messed me around so many times, they're just cr*p (and that's the nicest word I'm prepared to use! ) Getting some contact lenses will almost definately help you day to day, just don't put the wrong one in the wrong eye!