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 Orbit Eyelids and eyelashes Eyelids and eyelashes Women blink twice as often as men. Why do we blink? Conjunctiva Conjunctiva Lacrimal apparatus Lacrimal apparatus Extrinsic muscles Extrinsic muscles 3.04 Understand the functions and disorders of the sensory system 4 Interesting tidbit

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: window, permit passage of light rays; has touch and pain receptors that are sensitive to foreign objects entering the eye Cornea: window, permit passage of light rays; has touch and pain receptors that are sensitive to foreign objects entering the eye Iris: color muscle of eye, gets color from melanin pigment Iris: color muscle of eye, gets color from melanin pigment 2 intrinsic muscles: 2 intrinsic muscles: 1. Sphincter pupillae: constricts pupil 1. Sphincter pupillae: constricts pupil 2. Dilator pupillae: dilates pupil 2. Dilator pupillae: dilates pupil Pupil: dark circular structure inside iris Pupil: dark circular structure inside iris 3.04 Understand the functions and disorders of the sensory system 6

Understanding the functions of the eye Internal eye Ciliary body: smooth muscle holds lens in place with suspensory ligaments Ciliary body: smooth muscle holds lens in place with suspensory ligaments Lens: located behind iris and pupil; focuses images on retina; disc shaped with anterior and posterior convex shapes Lens: located behind iris and pupil; focuses images on retina; disc shaped with anterior and posterior convex shapes Aqueous humor: filled with watery fluid that is constantly replenished by blood vessels Aqueous humor: filled with watery fluid that is constantly replenished by blood vessels 3.04 Understand the functions and disorders of the sensory system 7

Understanding the functions of the eye Internal eye Sclera: white fibrous structure that maintains eye shape and protects delicate eye features below Sclera: white fibrous structure that maintains eye shape and protects delicate eye features below Choroid: blood vessels nourish the eye Choroid: blood vessels nourish the eye Retina: innermost coating of eye; light rays from an object form an image Retina: innermost coating of eye; light rays from an object form an image 3.04 Understand the functions and disorders of the sensory system 8

Understanding the functions of the eye Internal eye Vitreous humor: Vitreous humor: Filled with a jellylike substance; Maintains eyeball spherical shape and refracts (bends) light rays as they pass through the eye 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 Yellow disc that has a fovea centralis in the center containing the cones for color vision; the peripheral area contains rods for dim and peripheral 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

3.04 Understand the functions and disorders of the sensory system 14 Check your knowledge!

3.04 Understand the functions and disorders of the sensory system 15 Vision Activity Do you see what I see?

Disorders of the eye 3.04 Understand the functions and disorders of the sensory system 16 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 Describe this lens. Cloudy Cloudy Over 70 yrs age Over 70 yrs age Painless, gradual loss of vision and blurriness Painless, gradual loss of vision and blurriness Pupil changes from black to milky white Pupil changes from black to milky white 3.04 Understand the functions and disorders of the sensory system 17 Cataract

Disorders of the eye Cataract How is a cataract treated? Treatment: laser surgery and surgical removal of lens; post- operative contacts or eyeglasses 3.04 Understand the functions and disorders of the sensory system 18

Disorders of the eye Color blindness Do you see the number? Do you see the number? What is color blindness? Inability to distinguish colors What is color blindness? Inability to distinguish colors What causes it? Cone cells pick up shades of blue, red and green (cone cells cannot pick up these shades) What causes it? Cone cells pick up shades of blue, red and green (cone cells cannot pick up these shades) Who is most likely to have color blindness? Those with a family history Who is most likely to have color blindness? Those with a family history 3.04 Understand the functions and disorders of the sensory system 19

Disorders of the eye Conjunctivitis What is conjunctivitis? Inflammation of conjunctival membranes What is conjunctivitis? Inflammation of conjunctival membranes What are the symptoms? Redness, pain, swelling, and mucus discharge What are the symptoms? Redness, pain, swelling, and mucus discharge What causes it? bacteria What causes it? bacteria How is it treated? antibiotics How is it treated? antibiotics 3.04 Understand the functions and disorders of the sensory system 20

Detached retina 3.04 Understand the functions and disorders of the sensory system 21 Discuss what happens in this process. As a result of aging the vitreous humor constricts and pulls on the retina What is the relevance to health? Loss of vision Treatment: can be repaired with a laser or freezing if caught early

Disorders of the eye Diabetic retinopathy What causes diabetic retinopathy? Changes in the blood vessels in the retina What causes diabetic retinopathy? Changes in the blood vessels in the retina The blood vessels may swell or leak The blood vessels may swell or leak What are the symptoms? What are the symptoms? loss of vision or seeing red spots if bleeding occurs Explain the impact on vision. Explain the impact on vision. Leading cause of blindness in the US 3.04 Understand the functions and disorders of the sensory system 22

Disorders of the eyeGlaucoma What are the common symptoms of glaucoma? Excessive intraocular pressure resulting in destruction of retina & atrophy of the optic nerve. Then overproduction of the aqueous humor blocks flow of blood to venous circulation. What are the common symptoms of glaucoma? Excessive intraocular pressure resulting in destruction of retina & atrophy of the optic nerve. Then overproduction of the aqueous humor blocks flow of blood to venous circulation. How is it diagnosed? Tonometry, visualizing the optic nerve & central field testing should occur yearly for those over 40 How is it diagnosed? Tonometry, visualizing the optic nerve & central field testing should occur yearly for those over 40 Symptoms? Gradual mild achy feeling in eyes, loss of peripheral vision and seeing halos Symptoms? Gradual mild achy feeling in eyes, loss of peripheral vision and seeing halos How is it treated? Miotic drugs (constrict pupil and increase the outflow of the aqueous humor) or drugs to decrease the amount of aqueous humor produced How is it treated? Miotic drugs (constrict pupil and increase the outflow of the aqueous humor) or drugs to decrease the amount of aqueous humor produced 3.04 Understand the functions and disorders of the sensory system 23

Disorders of the eye Macular degeneration What is macular degeneration? Dimming or distortion of shapes primarily noticed when reading What is macular degeneration? Dimming or distortion of shapes primarily noticed when reading 2 Types: 2 Types: 1. Dry: thinning of retina; slowly progressive and no treatment; central vision may be greatly reduced 1. Dry: thinning of retina; slowly progressive and no treatment; central vision may be greatly reduced 2. Wet: new blood vessels grow behind the macula; causing leaking and bleeding distorting shapes; treatment: Avastin (injectable drug) inhibits protein that allows the destructive blood vessels to form 2. Wet: new blood vessels grow behind the macula; causing leaking and bleeding distorting shapes; treatment: Avastin (injectable drug) inhibits protein that allows the destructive blood vessels to form 3.04 Understand the functions and disorders of the sensory system 24

3.04 Understand the functions and disorders of the sensory system 25 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 26 Presbyopia: lens loses elasticity resulting in a decreased ability to focus on close objects; usually occurs after 40; correct with contacts or glasses Hyperopia (farsightedness): focal point beyond the retina because the eyeball is shorter than normal; objects must be moved farther away so that it may be seen clearly; correct with convex lens Myopia (nearsightedness): focal point is in front of the retina because the eyeball is elongated; bring objects closer to be seen clearly; concave lens to correct Amblyopia: reduction or dimness in vision Astigmatism: irregular curvature of the cornea or lens causes blurred vision and eye strain; eyeglasses with a special prescription to correct Diplopia: blurred vision Strabismus (cross-eyed): muscles of eyes do not coordinate their action; corrected by strengthening eye muscles and glasses

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 27

3.04 Understand the functions and disorders of the sensory system 28 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 29