3.04 Functions and disorders of the eye

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

2. 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

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

4. Understanding the functions of the eye External eye • Orbit-surrounds the eye to protect it • 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 • 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

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

6. 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

7. 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

8. 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

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

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

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

12. 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

13. 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

14. 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 14

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

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

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

18. 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

19. 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

20. Disorders of the eye Ishihara chart 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

21. 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

22. Disorders of the eye How is conjunctivitis spread? How can it be prevented? 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 22

23. 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

24. 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

25. Disorders of the eye Diabetics must have regular eye checks! 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 thesymptoms? No symptoms in early stages; in later stages may see red spots. • Explain the impact on vision. Leading cause of blindness in American’s. 3.04 Understand the functions and disorders of the sensory system

26. Disorders of the eye Tonometry 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? Miotic meds to decrease aqueous humor production 3.04 Understand the functions and disorders of the sensory system

27. 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

28. Problems with Focus 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

29. 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. 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 29

30. Testing vision What is the difference between an ophthalmologist and an optician? 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

31. 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

32. 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

33. 3.04 Functions and disorders of the eye The End 3.04 Understand the functions and disorders of the sensory system