3.04 Functions and
disorders of the eye
3.04 Understand the functions and
disorders of the sensory system
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3.04 Understand the functions and
disorders of the sensory system
Essential Questions
• What are the functions of the sensory system?
• What are some disorders of the sensory system?
• How are sensory system disorders treated?
• How do you relate the body’s communication to
the sensory system?
3.04 Understand the functions and
disorders of the sensory system
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Understanding the
functions of the eye
3.04 Understand the functions and
disorders of the sensory system
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Understanding the functions of the eye
External eye
Orbit-surrounds
protect it
Eyelids
the eye to
and eyelashes
Women blink twice as often as
men. Why do we blink?
Conjunctiva-sac
that lines the
eyelid and secretes mucus to
lubricate the eye
Lacrimal
apparatus(glands)secrete tears to cleanse and
moisten the eye; also contain
enzymes to fight bacteria; tears
drain into nasal cavity.
Extrinsic
muscles-moves the eye
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Understanding the
functions of the eye
External eye

Extrinsic
muscles
3.04 Understand the functions and
disorders of the sensory system
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Understanding the functions of the eye
Internal eye
Cornea-allows for
passage of light rays
Iris-controls
the
amount of light entering
the pupil
Pupil-regulates
the
amount of light passing
to the retina
3.04 Understand the functions and
disorders of the sensory system
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Understanding the functions of the eye
Internal eye
Ciliary body-holds the
lens in place
Lens-focuses
images on
the retina; this is known as
accommodation
Aqueous
humor-helps
maintain the shape of the
eyeball
3.04 Understand the functions and
disorders of the sensory system
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Understanding the functions of the eye
Internal eye
Sclera-maintains
eye
shape and protects
internal structures.
Choroid-contains
blood vessels to nourish
the eye
Retina-form
images of
objects
3.04 Understand the functions and
disorders of the sensory system
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Understanding the functions of the eye
Internal eye
Vitreous
humormaintains the
eyeball’s shape and
refracts light rays
3.04 Understand the functions and
disorders of the sensory system
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Understanding the functions of the eye
A yellow disc that
contains the cones for
color vision.
3.04 Understand the functions and
disorders of the sensory system
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Understanding the
functions of the eye
Process of Seeing

Trace the field of
vision.

Is there anything
strange about
this picture?
Explain
Why can’t you see in the dark?
3.04 Understand the functions and
disorders of the sensory system
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Understanding the
functions of the eye
Vision
What happens as you move
your paper away from and
toward to your eye?
3.04 Understand the functions and
disorders of the sensory system
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Understanding the
functions of the eye
Rods and cones of the retina
What are the functions of the rods and cones?
3.04 Understand the functions and
disorders of the sensory system
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Understanding the
functions of the eye
Rods and cones of the retina
*Rods-sensitive to DIM light;
help us to see at night.
*Cones-sensitive to BRIGHT light;
responsible for color vision.
3.04 Understand the functions and
disorders of the sensory system
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3.04 Understand the functions and
disorders of the sensory system
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Vision Activity
Do you see what I see?
3.04 Understand the functions and
disorders of the sensory system
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Disorders of the eye
Glaucoma
Diabetic retinopathy
Cataract
Have you heard of these conditions?
What do you know about them?
3.04 Understand the functions and
disorders of the sensory system
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Disorders of the eye
Cataract-the lens becomes cloudy
Common in people over
70 yrs. of age.
Causes a painless,
blurring or loss of vision,
may see halos around
lights at night.
3.04 Understand the functions and
disorders of the sensory system
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Disorders of the eye
Cataract
How is a cataract
treated?
Laser surgery or
surgical removal of
the lens; lens implant
3.04 Understand the functions and
disorders of the sensory system
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Disorders of the eye
Color blindness
Do
you see the number?
What is color blindness?
What causes it?
Cone cells do not work
properly; hereditary
Who is most likely to have
color blindness?
Affects 8-10% of the male
population
3.04 Understand the functions and
disorders of the sensory system
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Disorders of the eye
Hordeolum (aka sty)-tiny abcess at the base of an
eyelash
What
are the symptoms?
Eyelid is red, painful, swollen
How
is it treated?
Warm, wet compresses
to relieve pain and
promote drainage
3.04 Understand the functions and
disorders of the sensory system
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Disorders of the eye
Conjunctivitis-inflammation of the
conjunctival membrane;
aka “pink eye”
What
are the symptoms?
Redness, pain, swelling, discharge of
mucus; usually begins in one eye and
spreads to the other by a washcloth or
hands.
How is it treated?
Eyewashes and antibiotics
3.04 Understand the functions and
disorders of the sensory system
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Detached retina
Discuss what happens in this
process. The vitreous fluid
contracts with age and pulls
on the retina causing a tear.
What is the relevance to
health? May cause blindness
3.04 Understand the functions and
disorders of the sensory system
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Detached retina
Compare this process
to the previous picture.
What might cause this
condition?
Aging or a traumatic
injury to the eye
3.04 Understand the functions and
disorders of the sensory system
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Disorders of the eye
Diabetic retinopathy-caused by
changes in blood vessels in the
retina; blood vessels may swell
and leak or abnormal vessels
may grow on the retina
What are the symptoms?
No symptoms in early stages; in
later stages may see red spots.
Explain
the impact on vision.
Leading cause of blindness in
American’s.
Diabetics must have regular eye checks!
3.04 Understand the functions and
disorders of the sensory system
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Disorders of the eye
Glaucoma-overproduction of
aqueous humor causing
destruction of the retina and
atrophy of the optic nerve
What are the common symptoms of
glaucoma?
Mild aching of the eye, loss of
peripheral vision, halo around the
eye
How is it diagnosed?
Use of 3 tests to diagnose:
tonometry, opthalmoscopy, field test
How is it treated?
Tonometry
Miotic meds to decrease aqueous
humor production
3.04 Understand the functions and
disorders of the sensory system
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Disorders of the eye
Macular degeneration-occurs with
aging; straight lines look wavy, blind
spots appear.
Compare
the two types.
Dry-gradual thinning of the retina; central
vision decreases; no known treatment
Wet-new blood vessels grow behind the
macula and distorts its shape; treated with
injectable med (Avastin), laser surgery
How
is it diagnosed? On routine exam
the doctor notices yellow deposits under
the retina
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Compare the symptoms and treatments of these
common eye disorders.
Can a person have more than one of these disorders? Explain.
3.04 Understand the functions and
disorders of the sensory system
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Hyperopia-”farsightedness”; objects must be moved farther away
to be seen.
Myopia-”nearsightedness”; objects must be brought close to the
eye to be seen.
Presbyopia-the lenses lose their elasticity causing problems focusing
on close objects; usually occurs after the age of 40.
Astigmatism-irregular curvature of the lens or cornea; causes blurred
Vision; special eye glasses helps the condition.
Compare the symptoms and treatments of these
common eye disorders.
Can a person have more than one of these disorders? Explain.
3.04 Understand the functions and
disorders of the sensory system
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Testing vision

How do we test visual
acuity?

What is 20/20?

What does PERRLA
mean?
3.04 Understand the functions and
disorders of the sensory system
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Testing vision
Ophthalmoscope-lighted instrument
used to view the eye.
Ishihara-test for color-blindness
Snellen chart->>>>>>>>>>>>>>>>>>>>>>
Optician-a maker or dealer of lenses
or contacts
Ophthalmologist-specialist of the eye
3.04 Understand the functions and
disorders of the sensory system
31
3.04 Understand the functions and
disorders of the sensory system
Essential Questions
• What are the functions of the sensory system?
• What are some disorders of the sensory system?
• How are sensory system disorders treated?
• How do you relate the body’s communication to
the sensory system?
3.04 Understand the functions and
disorders of the sensory system
32
3.04 Functions and
disorders of the eye
The End
3.04 Understand the functions and
disorders of the sensory system
33