2. rhodopsin  retinal + opsin
Light adaptation
Dark adaptation

12. Sclera
Choroid
Rectus muscle
Retina
Ciliary muscle
Fovea
Optic disc
Aqueous humour
Conjunctiva
Optic nerve
Blood vessels
Cornea
Pupil
Vitreous humour
Canal of Schlemm
Lens
Iris
Suspensory ligament

14. Controlling light

15. Bright light Circular muscle contracts Radial muscle relaxes
Iris ring closes
Pupil is small

16. Dim light Circular muscle relaxes Radial muscle contracts
Iris ring opens
Pupil is large

18. Accommodation Rays from a point on a far object
Rays from a point on a near object

19. Far object Ciliary muscle relaxed Ciliary ring opens Ligaments go taut
Lens pulled flat

20. Near object Ciliary muscle contracts Ciliary ring closes
Ligaments go slack
Lens more spherical