The optic disc is a blind spot because no light receptor cells are present in this area of the retina where the optic nerve and retinal blood vessels leave the back of the eye.
视盘是个盲点，因为视网膜的这个区域没有光感细胞，视神经和视网膜血管从眼睛后面的这个部位伸出去。
2
The effective incident rays entered the eye from different parts of the reflection disc according to their incident angles.
有效投射光线依照其投射角，由光斑的不同部位进入眼中。
3
A curious trait they all share is that they have only one eye: a large, pupil-less disc, red and glowing.