Page 417 - Microsoft Word - LessonPlan-Overview.doc
P. 417
Unit 19: Biology Part 2 Page 72 of 137
Rods allow us to see in dim light, Vision Problems
while cones allow us to see light of
different colors. Do you or someone you know
where glasses or contact lenses.
Glasses and contacts are used to
correct vision problems. The two
most common eye problems are
myopia and hyperopia, and each is
fixed a different way.
Myopia is sometimes called
Figure 56: Rods allow us to see nearsightedness. About one third
in dim light while cones allow of people have this problem.
us to see in color. Myopia happens when the eye is
too long. With eye too long,
The Structure of the Eye images seen are focused a little bit
in front of the retina, instead of on
The eye is a complex structure that the retina as they would be in a
detects and focuses light. Light normal eye.
first enters the eye through the
cornea, a clear protective layer on
the outside of the eye. The pupil,
a black opening in the eye, lets
light in. In dark rooms, the pupil
will become larger, or dilate, in
order to let in more light. If the
room suddenly becomes bright, the
pupil will become smaller. The
pupil is surrounded by the brown,
blue, grey, or green iris.
Figure 57 – If a person has
After passing through the pupil, myopia, light focuses in front of
light goes to the lens which, like a the retina.
hand lens, is a clear curved
structure that helps focus light on People with myopia can see nearby
the retina, in the back of the eye. objects clearly. Objects that are
The retina is where the rods and far away, however, look blurry.
cones are found. This can be corrected with a
© 2011 Supercharged Science www.ScienceLearningSpace.com
819
