Medicaid pays for lenses and frames. They pay for whatever lenses you need, but they only pay for the cheapest junkiest frames. And they only pay for one pair of glasses every 2 years, unless you can prove your eyes are getting very rapidly worse.
So if the hinges on those cheap junky frames wear out in 3 months, as they always do, you are stuck without glasses for 21 months before you can get new glasses. If you say I want the better frames, I'll pay the difference, you can't get them. The optician is not allowed to do that. Nor, once you have told the optician you are on medicaid, are they allowed to sell you the lenses you need and the frames you want, for straight cash. They are only allowed to take medicaid from you -- no cash.
If you are a homeless person, and you need glasses to read and fill out a job application -- too bad. Furthermore, people believe that the reason you don't fill out job applications is that you are mentally ill, when the truth is, that you simply need glasses.