I have not found any unbiased reviews of eyeglass lenses on the web. (A google search will lead to all sorts of advertisements.) So let me share my experience with Accolade lenses manufactured by Essilor with anyone who needs progressive (bifocal) lenses. They are NOT GOOD! The progressive corridor is very small, meaning that vision in intermediate distances is poor. Moreover the transitions distorts the shape of the objects, making it difficult to get used to new lenses. The lenses are made of a polycarbonate material which is shatter-resistant but somewhat opaque, thus perhaps suitable for use during sports but not for reading, driving, or everyday use.
Additionally, Cambridge Eye Doctors mounted my lenses too low, with the axis slightly turned, and 1 mm off center. Taken together these small mistakes compound with mediocre optics to give a bad eyeglass experience.
My advice when buying eyeglasses, specially if you need high-diopter glasses or bifocals:
1 - Avoid chain eyewear stores. Linea Sella at Rua Melo Alves in São Paulo, Brazil, has never let me down. I also made good glasses at Clairmont-Nichols opticians (if I recall correctly) on 1st Ave in the Upper East Side in Manhattan. Otherwise my experiences in the US were with chains, none good. If you have suggestions, please comment.
2 - Spend more on high quality optics. I hear that Zeiss is the standard. Varilux also worked for me, though it is also manufactured by Essilor, the makers of Accolade. If there are any honest professional reviews out there, please let me know.