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视效率(Visual efficiency)是用来表达视力损失的程度,或作为评定眼残废等级的依据。它是根据中心视力的高低而分别计算出来的。当初Snell和Ster-ing二氏(1925)是先确定20/20(1.0)视力的视效率为100%,20/200(0.1)的视效率为20%,以后求取它们间(1.0～0.1)视效率的“几何增率”。我们知道1.0视力即1分最小分解角,0.1视力即10分最小分解角。后者比前者增加9分,但视效率却自100%减至20%,即后者的视效率为前者的1/5=0.2。由此可知视效率的几何增率该是0.2=0.836251031,也就是说最小分解角每增加1分,视效率就降到它原
Visual efficiency is used to express the degree of loss of vision or as a basis for assessing the degree of disability of the eye. It is based on the level of central vision were calculated separately. The original Snell and Ster-ing (1925) first determine the 20/20 (1.0) visual acuity was 100%, 20/200 (0.1) visual acuity was 20% ) The “geometric rate of efficiency”. We know that the minimum visual acuity of 1 point decomposition, 0.1 minimum visual acuity that is 10 points decomposition. The latter increased by 9 points compared with the former, but the visual efficiency was reduced from 100% to 20%, which the latter’s visual efficiency as the former 1/5 = 0.2. It can be seen that the geometric efficiency of visual efficiency is 0.2 = 0.836251031, which means that the minimum decomposition angle for each additional 1 point, as the efficiency dropped to its original