The last time I got eyeglasses, I made the stipulation to them that I wanted the best optical quality that I could get. Zeiss provides an
Abbe Number for their lenses so that you can see how much chromatic aberration they will have.
Here is one PDF file that has that information in it, on page 1.1:
http://www.vision.zeiss.com/41256820...SOLA_Specs.pdf
The higher the Abbe number, the better. Note that the trade-off is weight, as the best Abbe number available in eyeglasses can be had from crown glass, while resins tend to be lighter but not perform quite so well optically. While fluorite lenses would optically perform even better, I am not aware of anyone making them for eyeglasses.
Another thing you can see by looking at that chart is that, unless you are specifying your own lenses, you can end up with absolutly poor optical performance. The light weight, super high index of refraction lenses perform the worst visually, while they are the ones commonly used for stronger presciptions.
In my case, the CR-39 resin seems to have the best optical performance for its weight. Note that certain materials are not available beyond certain prescription limits, so if you have particularly bad eyesight you may need to make some tradeoffs.
Regards,
Eric