( A ) In front of the lens, the aperture surrounded by the iris, called the pupil, whose diameter is regulated by iris.
( B ) Photoreceptor cells rods and cones contain the light-sensitive proteins photopigments
( C ) The inner layer is the retina and it contains three layers of cells – from outside to inside – ganglion cells, bipolar cells and photoreceptor cells.
( D ) The daylight (photopic) vision and colour vision are functions of cones and the twilight (scotopic) vision is the function of the rods.
