Snell-Sterling visual efficiency scale

visual efficiency scale, Snell-Sterling

A representation of visual efficiency as a function of visual acuity, in which are taken into account other factors such as perception, experience, etc. in estimating how much vision a person has for a given visual acuity.

Table V2 Relationship between visual acuity and the Snell-Sterling visual efficiency scale (in percentage round figures)
visual acuity		Efficiency	loss of vision
(m)	(ft)	(in %)	(in %)
6/6	20/20	100	0
6/7.5	20/25	96	4
6/9	20/30	91	9
6/12	20/40	84	16
6/15	20/50	77	23
6/18	20/60	70	30
6/24	20/80	59	41
6/30	20/100	49	51
6/48	20/160	29	71
6/60	20/200	20	80
6/90	20/300	8	92
6/120	20/400	3	97
6/150	20/500	1.5	98.5