Page 261 - (DK) I Can’t Believe It! 2

TRUE OR FALSE? 259
Your irises Sight is the most important sense, enabling FAST FACTS

us to view the world. Light from exterior objects
is automatically focused onto a layer of light
are as unique receptors at the back of the eye. These receptors THE EYE CAN
DISTINGUISH BETWEEN
then send messages to the brain about the
UP TO 10 MILLION
patterns of light. The brain interprets these
messages, enabling us to see 3-D, moving
as your fingerprints color images of what is going on around us. DIFFERENT COLORS
Optic nerve carries nerve

signals from retina to the brain
Iris
Iris color is determined by the
light rays
pigment cells and connective Cornea bends
tissue—more pigment makes
the eyes browner, while less
pigment makes the eyes bluer.
Light rays
reflected
Eyelashes protect the from person
eye from any dust or
pollen that tries to enter. Lens fine- Upside-down
focuses light rays image on retina
The pupil is not a black circle but a hole in the
iris that lets light enter the eye. Light rays are
focused by the cornea and lens to produce an
image on the retina. We see in color because
light-sensitive cells in the retina respond to
different colors and send signals to the brain.
THERE ARE MORE
COLOR-BLIND
BOYS THAN GIRLS

BOYS: 8% GIRLS: 1%
People with red/green color blindness—
the most common form—find it hard to
distinguish colors that have a red or green
element to them. Color-blind people often
have an increased ability to spot camouflaged
objects, and excellent night vision.

The iris contains muscles that control
the levels of light entering the pupil.

US_258_259_309600_Eyes.indd 259 19/12/17 3:48 pm