was a huge bonus for insurance companies but cost far more to taxpayers and seniors than it covered. Nevertheless it helped many of us, especially with RX drugs. Medicare (and in most states Medicaid) does not cover glasses or exams (except after eye surgery or with severe eye diseases), dental, or hearing aids, services which are absolutely necessary to have any kind of decent life.
Many seniors simply live without teeth or dentures, in pain and unable to chew. A few private plans cover "dental health", meaning cleaning, Xrays, and checkups at a high cost. If you need extractions, crowns, implants, root canals they rarely cover any of the cost. In the case of hearing aids I have not heard of any affordable plans though loss of hearing leaves seniors isolated and in danger.
There are a few states where Medicaid covers some of these services but Repugs are trying to cut them out (as in N.Carolina.)
Some of us go to Canada or Mexico when we can. Dental care in Mexico is good and costs about 25% of US care.
If you have any good HMOs in your state your out of pocket fees will be less than on Medicare Supplement and they generally cover some preventive care.