The eye contains several parts that work together to allow vision. Light enters through the cornea and passes through the pupil, which is controlled by the iris and sized by the radial and circular muscles. The light then passes through the lens, which changes shape via the ciliary muscles and suspensory ligaments to focus the light onto the retina. The retina contains light-sensitive cells that transmit signals through the optic nerve to the brain. The fovea is the most sensitive part of the retina, forming clear images, while the blind spot lacks cells.

1. The eye
A window

2. Structure choroid
Black to absorb light
ciliary muscles
Changes the shape of lens
conjunctiva
protects the cornea
cornea
Transparent to allow light
lens
Bends the light onto
the retina
iris
Controls light entering the eye
suspensory
ligaments
Holds the lens in place sclera
Tough to keep shape of eye
retina
Contains light
sensitive cells
optic nerve
Transports the impulses to the brain
fovea
Most sensitive part,
clear image is
produced
Blind spot
no sensitive cells

3. Focusing light onto the retina
The light rays are bent at the cornea and the lens.

4. Pupil reflex
• In bright light:
• radial muscle relax and
circular muscles contract
to narrow the pupil. less
light enters the eye.
• This protects the retina
from damage.
• BRRCC
• In dim light:
• radial muscle contract
and circular muscles relax
to widen the pupil. More
light enters the eye.
• This helps a person see
better in the dark.
• DRCCR

5. Accomodation

6. Accommodation
looking at far/distant objects
• The ciliary muscle relaxes
• The lens is pulled into a thin shape
• This bends the light slightly
• The image is formed on the retina

7. Accommodation
looking at close/near objects
• The ciliary muscle contracts
• The lens becomes rounder
• This bends the light greatly
• The image is formed on the retina
Can you tell why your eyes feel tired
When you’re reading for a long time?
What can you do to rest your eyes?