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.
, R8 K) e+ L; O) ]1 o0 wvisual aids (glasses or contact lenses) must have vision of 20:20 (6:6) with both eyes open.
$ `+ @: a0 [# x" W- }% T7 ]
请问上面的意思是什么？相当于国内什么等级的视力？谢谢！