Hi Matt,
Glad to hear your buddy did well at the range. A few years ago, I had a double vision issue (not stroke) which was unable to be diagnosed. In order for me to function day to day I had to wear an eye patch. It solved alot of issues since my depth perception was off and I would frequently bump into things. Thankfully, in my case, my vision returned to normal.
Long story short, golf was difficult that summer, but manageable. I'm sure with some perseverance, your buddy will adapt well. I wish him well...