According to WHO, blindness is defined as a visual acuity of the better eye, less than
Blindness

WHO has proposed a uniform criterion and defined blindness as "Visual acuity of less than 3/60 or its equivalent".
In the absence of appropriate vision charts, the WHO has now added the "inability to count fingers in daylight at a distance of 3 meters" to indicates less than 3/60 or its equivalent.
6/60.
5/60.
4/60.
3/60.