The theory is that children are naturally far sighted which creates blurrier/lower contrast central vision and sharper/higher contrast peripheral vision. The brain interprets the higher contrast peripheral vision as a sign the eye is too short and far sighted, and the eye begins to grow. As the eye grows to the appropriate length, central vision experiences higher contrast and peripheral vision experiences lower contrast, and the eye stops growing.
If you degrade the peripheral vision's ability to experience higher contrast at all with these glasses, then the brain will never see a need to grow the eye.
https://assets.researchsquare.com/files/rs-1258672/v1/48b147...
Downsides were that in the US there were expensive, and need proper daily cleaning, but the tradeoff is worth it - only need 1 pair per year - less waste too!
Going to get Lasik this year because they don't play nicely with travel in developing countries, but they were absolutely fantastic for school and university.
One has to wear the contacts every night. They do not reverse myopia but are the most effective in stopping further progression of myopia. As per our eye doctor, ortho-K lens is the most effective (~80%) and is a non-destructive method unlike LASIK which basically burns the cornea to the right shape.
There is also a team at Univ. of Washington who designed glasses to slow down the progression of myopia (approved in Canada, not yet in the USA). https://newsroom.uw.edu/news/glasses-stop-myopia-are-success...