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.
$ ^$ w. |1 U" E7 ^4 R6 U! Cvisual aids (glasses or contact lenses) must have vision of 20:20 (6:6) with both eyes open.
+ i: i) h, W8 I8 \$ }$ R8 [
请问上面的意思是什么？相当于国内什么等级的视力？谢谢！