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.
visual aids (glasses or contact lenses) must have vision of 20:20 (6:6) with both eyes open.
0 x( j5 E+ u9 N1 o1 N. C$ E
8 b7 K7 s3 F2 }4 p' x请问上面的意思是什么？相当于国内什么等级的视力？谢谢！