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Objectives

Objectives. By the end of this presentation you will be able to: Recognize major components of the eye Have a basic understanding of how the eye works Understand how eye disease affects the components of the eye. The Eye.

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Objectives

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  1. Objectives • By the end of this presentation you will be able to: • Recognize major components of the eye • Have a basic understanding of how the eye works • Understand how eye disease affects the components of the eye

  2. The Eye • The eye allows us to see and interpret the shapes, colors and dimensions of objects in the world by processing the light they reflect or emit • The eye is able to see in bright or dim light, but it cannot see objects when light is absent

  3. The Eye When you look at any object • Light waves from that object enter the eye first through the cornea,which is the clear dome at the front of the eye • Light waves progress through the pupil, the circular opening in the center of the colorediris • Immediately behind the iris (and pupil) is the crystalline lens, and light passes through that also

  4. The Eye • Light waves are bent (converged) first by the cornea, then even more so by the crystalline lens, to a nodalpoint which is immediately behind the lens • At the nodal point, the light waves (image) become reversed (turned backwards) and inverted (turned upside down) • Light waves continue through the vitreous humor, the clear gel that makes up about 80% of the eye’s volume, and then back to a clear focus on the retina behind the vitreous • The small, central area of the retina is the macula; it provides the best vision of any location in the retina

  5. The Eye

  6. The Eye • The light impulses are changed into electrical signals, then sent through the optic nerve along the visual pathway to the occipital cortex, or posterior (back), of the brain • This is where the electrical signals are seen by the brain as a visual image • When light entering the eye is bright enough, the pupils will get smaller (constrict) due to pupillary light response

  7. The Eye Extraocular Muscles

  8. The Eye • Cardinal positions of gaze • Up/right • Up/left • Right • Left • Down/right • Down/left • In each position of gaze, one muscle of each eye is the primary mover of that eye, and is “yoked” to the primary mover of the other eye

  9. The Eye Strabismus, (cont’d) With strabismus, while one eye is fixating on a particular object, the other eye is turned in another direction, either inward (cross-eyed), outward (wall-eyed), upward, or downward • As a result, the person either experiences “diplopia” (double vision) or • the brain learns to turn off (suppress) the image of the strabismic eye to maintain single vision

  10. The Eye

  11. Hyperopia

  12. When the cornea is oblong shaped, it causes light rays to focus on two different points on the retina, instead of just one. As a result, people with significant astigmatism may have distorted or blurry vision.

  13. Astigmatism • Unequal curvatures in cornea & lens

  14. The Eye Miscellaneous tidbits about the eyes A newborn’s eyeball is about 18 millimeters in diameter, from front to back. It grows gradually to a length of approximately 24-25 millimeters (about 1”), or just smaller than a 1 1/2” ping pong ball!

  15. Diseases of the Eye Diabetic Retinopathy This is a complication of diabetes in which long-term exposure to high glucose levels in the blood has damaged retinal blood vessels. This results in new growth of abnormal blood vessels, fluid buildup in the macula (fovea), inadequate blood supply to the retina and possibly blood and fluid leakage into the retina and the vitreous body

  16. Diseases of the Eye • A cataract is a clouding of the eye's natural lens, which lies behind the iris and the pupil • The lens is mostly made of water and protein. • Protein may clump together and cloud • This is a cataract, and over time, it may grow larger and cloud more of the lens, making it harder to see

  17. Diseases of the Eye • Researchers are identifying factors that may cause cataracts such as: • People with diabetes • Users of steroids, diuretics, and major tranquilizers • Users of a lot of salt • Cigarette smoke • Air pollution • Heavy alcohol consumption

  18. Diseases of the Eye Glaucoma • Glaucoma represents injury to the optic nerve secondary to elevated pressure inside the eye. Conventional surgery to treat glaucoma makes a new opening in the meshwork. This new opening helps fluid to leave the eye and lowers intraocular pressure.

  19. The Eye http://www.cms.hhs.gov/MLNProducts/65_ophthalmology.asp http://www.cms.hhs.gov/MLNProducts/Downloads/internet_only_manuals.pdf Internet only manuals, coding http://www.visionchannel.net/diabeticretinopathy/ Great website for information http://www.bertscope.com/Literature/Lit_Requests/info_poster.html Free eye posters and online stuff http://www.optima-hyper.com/eyetests/fitness.htm Optima’s Eye Fitness Tests Resources:

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