an uncorrected visual acuity of at least 20/40 (6/12) with both eyes open. / T! O* X' F' f1 Y
visual aids (glasses or contact lenses) must have vision of 20:20 (6:6) with both eyes open. * [& j, J" P2 h4 S7 U8 `$ Z
; j. o/ ~2 n6 W+ p
请问上面的意思是什么?相当于国内什么等级的视力?谢谢!