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.
8 ^! f0 Z& K" x  _3 R3 Zvisual aids (glasses or contact lenses) must have vision of 20:20 (6:6) with both eyes open.
% e% |1 h# i) O/ P/ F9 m
. P: T9 R2 o, n+ i0 m请问上面的意思是什么？相当于国内什么等级的视力？谢谢！