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THE EYE

THE EYE. Bushong Ch. 29 p 358 - 359 Appendix #1 State Fluoro Syllabus pg 77 Reference: Ch. 14 Carltons. Early Fluoroscopy. The eyes are the window to the soul………. Red goggles for dark adaptation. Fluoroscopy was performed in total darkness

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THE EYE

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

  2. Early Fluoroscopy

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

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

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

  6. 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

  7. 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.

  8. 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

  9. 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 Visual Physiology 2 types of light receptors

  10. 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

  11. 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

  12. Eat the ice cream CONEin the DAYLIGHT!

  13. 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).

  14. 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

  15. 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.

  16. 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.

  17. 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

  18. 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

  19. 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

  20. 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

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

  22. 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)

  23. Now your turn..

  24. 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.

  25. CATARACS • Dangers of early fluoro • DOSE RESPONSE ??

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