[jsmith99]

Good lenses are important - I was sceptical but I'm much happier with my Seiko 1.74 double aspheric than with my old glasses which were Specsaver's 1.74 aspherics: flatter front and less distortion and rainbow effects (chromatic aberration). If you have money to burn you can also get personalised 'free form' lenses made using the same machines used for custom varifocals.

However this only becomes important if you have a strong prescription and buying online is dangerous if you have a strong prescription, especially astigmatism. You can send them your horizontal PD but they have no way of knowing the vertical component without seeing how the frames sit on your face (which depends on your nose and ears).

Some of the better online specialists will send you the frame with dummy lenses for you to mark your pupils on with a marker, and you then send them back to be glazed.