2.87 describe the structure and function of the eye as a receptor

The eye detects when light is strong/little and enlarges/shrinks the pupil when necessary (shrinking in bright light and enlarging in dim light)

Conjunctiva - this lubricates and protects the surface of the eye
Cornea - bends (refracts) light into the eye (it is transparent and has no blood vessels supplying it with oxygen so oxygen diffuses in from the outer surface)
Iris - this controls the diameter of the pupil, therefore it controls how much light enters the eye (big pupil = lots of light, little pupil = little light)
Lens - focuses the light onto the retina
Retina - the light-sensitive part of the eye. It is covered with  light receptors known as rods and cones (rods are more sensitive in dim light but cannot see colour, cones are sensitive to colours but are not very good in dim light, cones are found all over the retina but mostly at the fovea)
Optic nerve - this carries impulses to the brain

image credit: BBC

notes credit: CGP