Many people with MS get diplopia, and so need prismatic lenses to help with the double vision.

He passed away ten years ago, the glasses were custom-made in 70's or so. He'd close one eye and use the other (better suited for this). He'd have tremors, including in the eyes. Reading made him very tired, eventually a friend would read complex beta literature before him. To me (as kid) the glasses felt like a huge looking glass.

A friend of my parents also made a custom card deck, with huge symbols and letters. That way, we could work around his disability. We always had to work around his disability, and it regressed but slow variant and he was also too old to get the medicine which effectively stopped the MS from getting worse. However, it meant other people who had the quick version or were younger got more QoL.

I don't think he ever used Calibri. I mean, at that time, he wasn't into computers anymore. He had all kind of health isssues due to MS. It pains me to think people like him now have more difficulty to read letters because of BS decisions like these just cause NIH or whatever the silly reason must be. But there's also good news: if it is digital, they can override the font and such.