Answering calls if you are blind? Can Siri help?

I've been trying to help an elderly friend who is quickly losing what is left of his sight with his Mac, iPad and iPhone. We had hoped that the assistive features and Siri would be of great use, but assistive touch is way way too cumbersome for him to understand (I can barely understand it and I can see and have lots of Apple product experience) and Siri is often less than helpful. A disappointment.

But the most frustrating thing right now is that his vision has gotten so bad that he can't make out the green answer button to touch when a call comes in and he is missing all his calls. He can call me with Siri by saying "Call Doug" but he is so frustrated by not being able to answer calls he is practically in tears.

Apple didn't help with the latest upgrade by turning the slide to answer (which he was able to do) into a small green button which he can't find.

Note to Apple (and yes, I will give "feedback" on this) - please think about your senior citizen users before you go switching the UI on them!

Anyway, what I wanted to know is if there are any Siri ways of answering a call when it comes in. Or alternative ways of answering the phone which don't require being able to see the screen. He knows how to find and press the Home button and wait for the "ping" sound before giving a Siri command.

Thanks,

Doug