> For instance, orthokeratology contact lenses improve vision by temporarily squishing the cornea into a different shape, reminiscent of how ancient Chinese sol

> For instance, orthokeratology contact lenses improve vision by temporarily squishing the cornea into a different shape, reminiscent of how ancient Chinese soldiers are said to have slept with sandbags over their eyes for the same effect. This is a fascinating historical tidbit and I'm curious to learn more, but Google fails me. Did ancient Chinese soldiers do this specifically to improve their vision? Was myopia a big problem among those soldiers?