3.04 Functions and disorders of the eye 3.04 Understand the functions and disorders of the sensory system 1

2 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?

Understanding the functions of the eye 3.04 Understand the functions and disorders of the sensory system 3

Understanding the functions of the eye External eye Orbit-surrounds the eye to protect it Orbit-surrounds the eye to protect it Eyelids and eyelashes Eyelids 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 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. 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 Extrinsic muscles-moves the eye 4

Understanding the functions of the eye External eye Extrinsic muscles Extrinsic muscles 3.04 Understand the functions and disorders of the sensory system 5 Which extrinsic muscle allows you to look upward?

Understanding the functions of the eye Internal eye Cornea-allows for passage of light rays Cornea-allows for passage of light rays Iris-controls the amount of light entering the pupil Iris-controls the amount of light entering the pupil Pupil-regulates the amount of light passing to the retina Pupil-regulates the amount of light passing to the retina 3.04 Understand the functions and disorders of the sensory system 6

Understanding the functions of the eye Internal eye Ciliary body-holds the lens in place Ciliary body-holds the lens in place Lens-focuses images on the retina; this is known as accommodation Lens-focuses images on the retina; this is known as accommodation Aqueous humor-helps maintain the shape of the eyeball Aqueous humor-helps maintain the shape of the eyeball 3.04 Understand the functions and disorders of the sensory system 7

Understanding the functions of the eye Internal eye Sclera-maintains eye shape and protects internal structures. Sclera-maintains eye shape and protects internal structures. Choroid-contains blood vessels to nourish the eye Choroid-contains blood vessels to nourish the eye Retina-form images of objects Retina-form images of objects 3.04 Understand the functions and disorders of the sensory system 8

Understanding the functions of the eye Internal eye Vitreous humor- maintains the eyeball’s shape and refracts light rays Vitreous humor- maintains the eyeball’s shape and refracts light rays 3.04 Understand the functions and disorders of the sensory system 9

Understanding the functions of the eye 3.04 Understand the functions and disorders of the sensory system 10 A yellow disc that contains the cones for color vision.

Understanding the functions of the eye Process of Seeing Trace the field of vision. Trace the field of vision. Is there anything strange about this picture? Explain Is there anything strange about this picture? Explain 3.04 Understand the functions and disorders of the sensory system 11 Why can’t you see in the dark?

Understanding the functions of the eye 3.04 Understand the functions and disorders of the sensory system 12 What happens as you move your paper away from and toward to your eye? Vision

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 13 Understanding the functions of the eye

Rods and cones of the retina 3.04 Understand the functions and disorders of the sensory system 14 Understanding the functions of the eye *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 15 Check your knowledge!

3.04 Understand the functions and disorders of the sensory system 16 Vision Activity Do you see what I see?

Disorders of the eye 3.04 Understand the functions and disorders of the sensory system 17 Cataract Glaucoma Hyperopia Myopia Presbyopia Astigmatism Diabetic retinopathy Detached retina Have you heard of these conditions? What do you know about them? Color blindness Conjunctivitis

Disorders of the eye 3.04 Understand the functions and disorders of the sensory system 18 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.

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 19

Disorders of the eye Color blindness Do you see the number? Do you see the number? What is color blindness? What is color blindness? What causes it? What causes it? Cone cells do not work properly; hereditary Who is most likely to have color blindness? 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 20

Disorders of the eye Hordeolum (aka sty)-tiny abcess at the base of an eyelash What are the symptoms? What are the symptoms? Eyelid is red, painful, swollen How is it treated? How is it treated? Warm, wet compresses to relieve pain and promote drainage 3.04 Understand the functions and disorders of the sensory system 21

Disorders of the eye Conjunctivitis-inflammation of the conjunctival membrane; aka “pink eye” What are the symptoms? 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? How is it treated? Eyewashes and antibiotics 3.04 Understand the functions and disorders of the sensory system 22

Detached retina 3.04 Understand the functions and disorders of the sensory system 23 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 24 Detached retina Compare this process to the previous picture. What might cause this condition? Aging or a traumatic injury to the eye

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? What are the symptoms? No symptoms in early stages; in later stages may see red spots. Explain the impact on vision. Explain the impact on vision. Leading cause of blindness in American’s Understand the functions and disorders of the sensory system 25 Diabetics must have regular eye checks!

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? What are the common symptoms of glaucoma? Mild aching of the eye, loss of peripheral vision, halo around the eye How is it diagnosed? How is it diagnosed? Use of 3 tests to diagnose: tonometry, opthalmoscopy, field test How is it treated? How is it treated? Miotic meds to decrease aqueous humor production 3.04 Understand the functions and disorders of the sensory system 26

Disorders of the eye Macular degeneration-occurs with aging; straight lines look wavy, blind spots appear. Compare the two types. 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 How is it diagnosed? On routine exam the doctor notices yellow deposits under the retina 27

3.04 Understand the functions and disorders of the sensory system 28 Compare the symptoms and treatments of these common eye disorders. Can a person have more than one of these disorders? Explain. Problems with Focus

3.04 Understand the functions and disorders of the sensory system 29 Compare the symptoms and treatments of these common eye disorders. Can a person have more than one of these disorders? Explain. Problems with Focus 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.

Testing vision How do we test visual acuity? How do we test visual acuity? What is 20/20? What is 20/20? What does PERRLA mean? What does PERRLA mean? 3.04 Understand the functions and disorders of the sensory system 30

Testing vision 3.04 Understand the functions and disorders of the sensory system 31 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 32 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 Functions and disorders of the eye The End 3.04 Understand the functions and disorders of the sensory system 33