i dont like to contradict anyone, but I really wouldn't just go to the supermarket and buy off the peg glasses, although you think they are ok for you they could be straining your eye muscles and you maybe wouldn't realise it, also, the opticians usually look right into the eye and see the back of the eye too, this can detect any thing that may be at fault way before it could become a problem, so , pluck up the courage, go and get checked , you will have piece of mind and a lovely new pair of specs to show.