A unit of retinal illumination, equal to the amount of light that reaches the retina through1 square millimeter of pupil area from a surface having a brightness of1 candela per square meter.

• 光度视网膜亮度单位，相当于每平方米有一烛光亮度的表面，通过一平方毫米的瞳孔区域，到达视网膜的光线数量