Hi guys. My wife is a lab manager for a well known opticians so here is my take. If you don't get on with the varifocals take them back and tell them. They should let you go to bifocal or get 2 different pairs and refund etc. Some people just don't get on with them and my wife's company did this as often as needed. The pound shop glassss are fine for small time frames but no good for you needing them on for more than 20 to 30 mins. As said before, the strength is the same is both lenses but also the pupil distance is not specific to the person. This induces prism which can cause eye strain, headaches and the like. As for online spec makers, you do it at your own risk . Most opticians will not give your pupil distance with a prescription as they are not then resposible for the glasses you get from a different company. As above the pupil distance is very important for prism etc and as well as headaches, if you use for driving they could be dangerous. Think of it this way, would you buy a helmet online without ever trying the model on? The eyes are probably the most important sense to someone and putting in the hands of people with incomplete information is asking for trouble imo. If you can get a professional to do your pupil distance then all should be fine. However bear in mind my wife had to sign every pair of glasses off to the prescription and this is legally binding. If someone was in a car accident and the glasses weren't right she would end up in court. Not sure if the online guys would be as stringent. Basically get your glasses from a reputable optician Rich