I had used reading glasses and bi-focals with no problems, but then I recently got some varifocals and try as I might I couldn't get used to them and seemed to be suffering from something akin to sea-sickness whilst at the same time everything with parallel sides eg doorways, windows, TV screen etc was completely skewed so that eg a square looked like a rhombus. I returned to opticians who got a different person to re-test my eyes and lo and behold I had been given the wrong prescription. However, even after a re-make of the specs things weren't OK and I ended up with two pairs of specs instead of the varifocals, so now its always a case of 'The Wrong Glasses'! On a serious note I have since discovered four other people who have had similar problems with this same chain of opticians - I won't be going back there again!