Opticians are, in my experience, hacks, ...
I don't get this. Surely if you go to an reasonable optician and insist that you're not going to leave until you can see acceptably, you're not going to leave with anything less than an acceptable prescription? Admittedly my myopia and astigmatism are quite mild, but I've never had a glasses prescription that is gives me anything less than perfectly crisp vision. 
I've never had the same prescription twice in a six month period! What looks acceptable through tiny lenses in an optician's office is often awful in a real pair of glasses. Also, being longsighted, my eyes will accommodate for weak prescriptions...but will lose all close-up ability.
The prescription cycling glasses turn out to be unsuitable, btw. The curved frames just don't suit corrective lenses and distortion is terrible when riding - I feel 12 feet tall and judging sideways clearance (bastard barriers on psyclepaths!) is tricky. There is a money back guarantee so I'll get them to check they have made them correctly and, if they have, swap them for something more conventional (maybe with a cord, just in case). My "normal" glasses are absolutely fine for cycling, with no distortion, except that they're not as secure.
