1. 1 THE EYE Bushong Ch. 29 p 358 - 359 Appendix #1 State Fluoro Syllabus pg 77 Reference: Ch. 14 Carltons

2. 2 Early Fluoroscopy

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5. 5 The eyes are the window to the soul……….

6. 6 Red goggles for dark adaptation Fluoroscopy was performed in total darkness so the eyes had to be adjusted for 20 - 30 minutes by wearing red goggles

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8. 8 FOVEA CENTRALIS CENTRAL PART OF RETINA CONES TIGHTLY PACKED REMAINDER – CONES DIMISH = MORE RODS

9. 9 Human Vision Light passes through the lens, where light is focused onto the retina. Between the cornea and the lens is the iris, which acts like a camera diaphragm = controls the amount of light admitted into the eye

10. 10 the retina The retina is important because it contains the rods and cones. The sharpest point of vision is located in the center in an area called the fovea centralis.

11. 11 RETINA contains millions of specialized photoreceptor cells called rods and cones That convert light rays into electrical signals that transmitted to the brain through the optic nerve. Rods see in dim light and Cones provide the ability to see in color

12. 12 Visual Physiology 2 types of light receptors RODS NIGHT VISION SCOTOPIC PERCEIVE GRAYS PERIPHERY OF RETINA = DIM OBJECTS SEEN BETTER – 1000 X MORE SENSITIVE 30 min dark adaptation CONES DAYLIGHT PHOTOPIC PERCIEVE COLOR CENTER OF RETINA BETTER VISUAL ACUITY New II much brighter

13. 13 The rods These are located at the periphery of the retina There are fewer of them and they are sensitive to low levels of light. Night vision (scotopic vision) uses the rods of the eye to see The rods are colorblind

14. 14 The cones Cones are located at the center of the retina in the fovea centralis They respond to intense light levels. As such, these are used for our daylight (phototropic vision). Cones have better visual acuity and better contrast perception. Cones perceive color

15. 15 Eat the ice cream CONE in the DAYLIGHT!

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17. 17 Macula & Fovea centralis The macula, located in the center of the retina, is where most of the cone cells are located. The fovea, a small depression in the center of the macula, has the highest concentration of cone cells. The macula is responsible for central vision, seeing color, and distinguishing fine detail. The outer portion (peripheral retina) is the primary location of rod cells and allows for night vision and seeing movement and objects to the side (i.e., peripheral vision).

18. 18 CORNEA The cornea is a thin transparent protective covering that protects the eye. It has no blood vessels and it helps focus light onto the retina Light rays bounce off all objects. If a person is looking at a particular object, such as a tree, light is reflected off the tree to the person's eye and enters the eye through the cornea

19. 19 IRIS located between the cornea and the lens colored part of the eye It controls the amount of light that is admitted to the eye by dilating or constricting the pupil. Bright light causes contraction of the iris allowing only a small amount of light to hit the pupil In dim light, the pupil enlarges to allow more light to enter the eye.

20. 20 IRIS The structure which gives the "color" to the eye. The pupil is the hole in the iris. Contraction of the iris makes a pupil small. Relaxing of the iris makes the pupil large.

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22. 22 LENS & PUPIL focuses the light that passes through the pupil onto the retina where the light receptors are located The pupil is the opening to the eye. As the iris opens and closes, it causes the pupil to dilate or contract. Light has to pass through the pupil to reach the retina

23. 23 VISUAL ACUITY ABILITY TO PERCEIVE FINE DETAILS INTEGRATION TIME = 0.2 SEC (how long it takes to identify something) Photopic acuity is 10 x greater than scotopic Contrast perception is our ability to detect differences in brightness Normal viewing distance 12 – 15 inches

24. 24 Binocular vision is the best we can see at and is 12-15 inches from the object we are looking at. We have a blind spot at about 9 inches and can’t see from the periphery of the eye. Remember… integration time: 0.2 sec. and it is the ability to see and recognize everything we will

25. 25 VISION EYE SEES 32 SHADES OF GRAY COMPUTER 256 – 8 bit to 1024 12 bit depth SHADES REGARDING CINE: 32 FRAMES SOME FLICKER (OLD MOVIES) 60 FRAMES = NO FLICKER

26. 26 The Eyes & Radiation Dose What is the allowable annual limit for the eyes? _______________________ What problems with the eyes were seen with early Radiologists?

27. 27 The Eyes & Radiation Dose Cataracts (cataractogenic effects) P49 RAD – RHB SYLLABUS Formation of Cataracts – dose of several 110 rads Fibers in lens of eye are specialized to transmit light Damage to these (particularly to the developing immature cells – can result in cataracts)

28. 28 Now your turn..

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30. 30 The Early years Because of the high dose to the patient and to the operator’s eyes, radiation damage was noted shortly after the invention. Thomas Edison noted that his vision was deteriorating because of the radiation. The possibilities of this new find outweighed the dangers.

31. 31 CATARACS Dangers of early fluoro DOSE RESPONSE ??

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