请教这里的视力标准如何换算成国内的数值？

nils_li

an uncorrected visual acuity of at least 20/40 (6/12) with both eyes open.
6 B% i: _5 q' p6 Q/ F2 L' @visual aids (glasses or contact lenses) must have vision of 20:20 (6:6) with both eyes open.
* W: X5 X- l5 A8 b
, }0 U  v! s+ I, B: ~: `请问上面的意思是什么？相当于国内什么等级的视力？谢谢！