A lot of big brands have secret discount codes and loopholes that the general public may not know about, but if you've worked at a department store for any extended amount of time then you likely know some of the workarounds.
Ideally, the public would know all of the deals and offers at their disposal, but a lot of companies like to keep their return policies and special deals somewhat concealed (unless it's a big one-off sale), so that people don't abuse them (aka get their money's worth).
The following will get you significant discounts at LensCrafters: AAA (30% even on non-prescription sunglasses), AARP, Eyemed, Aetna, United Healthcare, Horizon BCBS of NJ, Empire BCBS, Health Net Well Rewards, Cigna Healthy Rewards. They tend to keep some of them quiet.
If you've bought photochromatic (lenses that get dark in the sun, like Transitions) lenses from LensCrafters and they appear to be peeling, bubbling, or otherwise looking weird, you're entitled to a free replacement because the lenses are delaminating, which is a known defect.