The cornea refracts light into the eye. It is transparent and has no blood vessels to supply it with oxygen, so oxygen diffuses in from the outer surface
Iris
It controls the diameter of the pupil and therefore how much light enters the eye
Lens
It focuses light onto the retina
Optic nerve
It carries impulses from the receptors to the brain
Adjusting for bright light
Very bright light triggers a reflex that makes the pupil smaller, allowing less light in
Adjusting for dim light
The brain tells the radial muscles to contract, which makes the pupil bigger
Focusing on distant objects
The ciliary muscle relaxes allowing the suspensory ligaments to tighten. The lens becomes less curved so it refracts light by a smaller amount.
Focusing on near objects
The ciliary muscle contracts which allows the suspensory ligaments to slacken. The lens then becomes more curved which increases the amount by which it refracts light.
