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Lab 35

Lab 35. Visual Tests and Demonstrations. Objective. SWU : how vision disorders are tested for SW : conduct tests used to evaluate visual acuity, astigmatism and color vision. Visual Tests and Demonstrations. Lab 36. Objectives.

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Lab 35

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  1. Lab 35 Visual Tests and Demonstrations

  2. Objective SWU: how vision disorders are tested for SW: conduct tests used to evaluate visual acuity, astigmatism and color vision

  3. Visual Tests and Demonstrations Lab 36

  4. Objectives • Conduct the tests used to evaluate visual acuity, astigmatism, and the ability to accommodate for close vision • Demonstrate the blind spot, photopupillary reflex, accommodation pupillary reflex, and convergence reflex

  5. Visual Acuity Snellen eye chart • Based on 20 feet in the United States (6m internationally). • 20/20 normal vision. • 20/70 worse than average vision. • 20/12 better than average vision. • TenSloan letters C, D, E, F, L, N, O, P, T, Z. • 20/200 Largest letter = legally blind

  6. 20/20 Vision—What is it?1m22s https://www.youtube.com/watch?v=48XD7Z9_XXs

  7. Visual Acuity Directions: Snellen Eye Chart Have your partner stand 20 feet in front of the Snellen chart (marked on floor) 2. Cover left eye with a 3x5 index card 3. Read the smallest set of letters possible 4. Record visual acuity value for that set of letters in Part A 5. Repeat the procedure using the right eye

  8. Astigmatism • Blurred vision due to irregular shape of the cornea • Common

  9. What is astigmatism?47s http://www.youtube.com/watch?v=B4P3f7ARLqU

  10. Astigmatism Test Have your partner stand 20 feet in front of the chart Cover left eye with a 3x5 card Focus on the spot in the center of the radiating lines Report which lines, if any, appear more sharply focused and darker Repeat the procedure using the left eye Record results in Part A of the lab report

  11. Accommodation • Lens changing shape when eye is focused for close vision • Muscles contract • Decreases with age

  12. Accommodation2m5s http://www.youtube.com/watch?v=p_xLO7yxgOk

  13. Accommodation Test • Hold the end of a meter stick against your partner’s chin so that the stick extends outward • Have your partner close the left eye • Hold a 3x5 card with a word written in the center at the far end of the meter stick • Slide the card along the stick toward your partner’s open eye, and locate the point closest to the eye where your partner can still see the letters of the word sharply focused • This is the “near point of accommodation” • 5. Record results in Part A of the lab report • 6. Repeat the procedure with the right eye closed

  14. Blind Spot • Caused by the optic disk (where the optic nerve meets the eye)

  15. Blind-Spot Demonstration Close your left eye, hold the index card about 34 cm away from your face Stare at the + sign in the figure with your right eye Move the figure closer to your face as you continue to stare at the + until the dot on the figure suddenly disappears Measure the distance using a meter stick Repeat the procedures with your right eye closed Record results in Part B of the lab report

  16. Color vision • Lack certain cones • Sex-linked trait • More common in males • 7% vs 0.4% in females • Stand 30 inches from chart http://www.color-blindness.com/ishihara-38-plates-cvd-test/#prettyPhoto/0/

  17. 1. Ishihara Color Blindness Test Go to www.color-blindness.comhttp://www.color-blindness.com/ishihara-38-plates-cvd-test/#prettyPhoto/0/ The Ishihara Test is the most well known color blindness test all around the world. It consists of 38 so called pseudoisochromatic plates, each of them showing either a number or some lines. This test can only be used to detect red-green color blindness. How the test works:For each plate you have to either enter the number or you have to choose the number of lines you can see. If you don't see anything just leave the input field empty.

  18. 2. F-M 100 Hue Test • This famous color vision test—which is based on 88 colored plates and not 100 as the name suggest—was introduced in 1943 by Farnsworth. • The test will show you four batches of 22 mixed colored plates. • Arrange the for rows of plates in a correct order • The higher your TES is, the more severely colorblind you are. Lower numbers are better! If you score above 70, you may have a color vision deficiency

  19. 3. Color Arrangement Test • In 1947 Farnsworth released the D-15 dichotomous test. This is to this day one of the most famous color vision deficiency test and definitely the most famous color arrangement test. • You simply have to arrange the given colors in the correct order of colors..

  20. 4. RGB Anomaloscope Test • Just match the left color to the right one using the slider below the box. • Click “Match Ok” or “No Match Possible”

  21. Photopupillary reflex Ask your partners to sit with his or her hand thoroughly covering his or her eyes for 2 minutes Position a flashlight toward a hand that covers the eye Ask your partner to remove 1 hand quickly Observe the pupil and note any changes in its size Have your partner remove the other hand, but keep the beam of light off of that uncovered eye Observe both pupils and note any differences in size

  22. Accommodation Photopupillary reflex • Have your partner stare at some dimly illuminated object in the room that is more than 20 feet away • Observe the size of the pupil of one eye • Then hold a pen/pencil about 25 cm in front of your partner’s face, and have your partner stare at it. • Note any change in the size of the pupil

  23. Convergence Reflex • Repeat the procedure above (accommodation pupillary reflex) • Note any changes in the position of the eyeballs as your partner changes focus from the distant object to the pencil/pen • Complete part B of the lab report

  24. Eye Disorder Case Studies This is a collection of case studies to help you get an insight on the typical history and initial examination of various ophthalmic disorders. The discussion, although brief, is intended to give you a simple overview of each disease

  25. Directions With a group of three please complete 5case study reviews • HISTORY Give a brief review of the patient’s history (why are they going to the eye doctor) • Exam findings(abnormalities?) • Diagnosis • Treatment OD ………………… oculus dexter (the right eye)OS ………………… oculus sinister (the left eye)OU ………………… oculus uterque (both eyes) IOP………………….intraocular pressure TONO- test for IOP Amsler Grid………...detects macular degeneration & retinal changes Slit lamp exam (SLE)………allows examination of the anterior portion of the eye Dilated fundus Exam (DFE)…medicine dilates the pupil for evaluation of internal eye health Wnl…………………..within normal limits CVF…….central visual field EOM………..extraocular muscles

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