Father driving with bad eyesight. What can I do?

Go to your motor vehicle state website and search "driver evaluation". There should be a form you can fill out asking for an evaluation of his driving ability.
Now if his MD says he should not drive, take his car away.

Your dad may be refusing to use a cell phone because he doesn't know how to work it.

If you think your dad is a danger to himself and/or others while he's behind the wheel yet he continues to drive you may have to force the issue. When I thought it was time for my dad to stop driving I took advantage of a Dr.'s appointment he had coming up. When we got there I passed a short note to the nurse about my dad's driving and that I wanted his Dr. to recommend that he not drive anymore. When we were with the Dr. the Dr. advised my dad to stop driving and as tough as it was on my dad he went along with the Dr.'s advice and I didn't have to be the bad guy.

Sometimes our parents have to be forced to stop.