As soon as you want to. We teach kids who have a ton of vision Onm in preparation of losing their vision in the future. Go to your local commission for the blind. You have a qualifying condition for them to start giving you services as soon as you would like to start them

Usually people end up calling O&M specialists when they have safety concerns. The big ones are having difficulty seeing in the dark, having difficulty seeing drop offs (curbs, stairs, etc) and bumping into things.

Keep in mind that it isn't just your own safety you have to consider sometimes, but also children. I had a client who had a baby, and they were wearing the baby strapped to their chest, and they walked into a glass door. The baby wasn't injured, but it could also easily have been a metal pole. That was what prompted him to seek training.

Getting training while you have some vision does make some things easier, such as the layout of accessibility features.

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In my opinion asap, you may be able to get certain concepts better with what sight you still have.

Training should be done using blindfolds. This will allow you to learn how to rely on the cane. The cane is a simple tool, people who are completely blind or low visioned use it to walk safely.