@hazardwarning It sounds like you're an interesting test case for eye problems. They should get students to study your eyes. I've never heard of those pigment problems. I'm glad they don't bother you much.
It is a shame that sight keeps changing. Like I said to the optician, I'm not keen on spending £350 every two years on specs. There are some theories out there that you can train short/long-sightedness out of your eyes with eyes exercises done over a long period of time. The fact that sight is very changeable might lend weight to that idea. In fact, my grandad did this himself in old age. I don't know all the details of what he did but part of it was putting a hand over one eye and gradually trying hard to focus on something he struggled to see with the other eye. He read about the exercises in a book and he said he did have some success with it but it was very time-consuming and didn't improve quickly.