Varifocal spectacles need to fit precisely on your nose and any tiny degree out will affect your vision. I bought two pairs from Specsavers on buy one get one free. One pair took me about a week to get used to, but the other pair, a different style, I'm still struggling with. I suggest going back to the opticians and explaining, get a refit and if that does not work then ask to try a different frame. Most Opticians, including the high street names, will change your frames free of charge if you can't get on with them.