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The Human Eye
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- 2. The Human Eye •Refractive index of lens different for each wavelength (colour) • Cool colours (blues) appear closer; warm colours (reds) further away • Agree?
- 3. Most people seethe red, Closer than the blue. Others see the opposite. How about you?
- 4. The Human Eye •Your eyes are about to get a workout. Have you stretched your eye muscles yet? • No? Then do that now!
- 5. Are you seeingspots?
- 7. Look at thecross for 10 seconds. What do you see?
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- 21. Reading What is wrongwith with this sentence? Aoccdrnig to rscheearch at Cmabrigde Uinervtisy, it deosn't mttaer in waht oredr the ltteers in a wrod are, the olny iprmoetnt tihng is taht the frist and lsat ltteer be at the rghit pclae. The rset can be a toatl mses and you can sitll raed it wouthit a porbelm. Tihs is bcuseae the huamn mnid deos not raed ervey lteter by istlef, but the wrod as a wlohe.
- 23. Do you seethe rabbit or the duck?
- 24. Read This OutLoud
- 25. Are You Sure?Read it again
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- 28. Structure & Function •IRIS – colored part of eye – controls light entering • PUPIL – black hole in iris – where light enters
- 29. Structure & Function •SCLERA – whites of the eye – supports eyeball – provides attachment for muscles • LENS – converging lens – allows us to see objects near and far
- 30. Structure & Function •CORNEA – transparent bulge over pupil – focuses light (refracts) onto retina • RETINA – internal membrane – contain light-receptive cells (rods & cones) – converts light to electrical signal
- 31. Blind Spot • Onretina where optic nerve leads back into the brain • No rod or cone cells • Other eye compensates for this area • Try this test to prove you have a blind spot…
- 32. Close left eyeand approach screen while staring at the letters…watch the dot!
- 33. Structure & Function OPTICNERVE • Transmits electrical impulses from retina to the brain • Creates blind spot • Brain takes inverted image and flips it so we can see
- 34. Structure & Function •RODS – 120 million cells – detect brightness (black & white) – for night vision • CONES – 6 million cells – detect color (RGB) – GANGLION CELLS – Detect movement and patterns
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- 36. Video • YouTube “The HumanEye” and “How the Human Eye Works”
- 37. Focusing Problems HYPEROPIA • Far-sightedness •Problem seeing close objects • Distance between lens and retina too small • Light focused behind retina • Corrected with converging lenses
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- 39. Focusing Problems PRESBYOPIA • Formof far-sightedness • Harder for people to read as they age • Lens loses elasticity • Corrected by glasses with converging lenses
- 40. Focusing Problems MYOPIA • Near-sightedness •Problem seeing objects far away • Distance between lens and retina too large • Light focused in front of retina • Correct with diverging lenses
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- 42. Diseases of theEye ASTIGMATISM • Eye cannot focus an object’s image on a single point on retina • Cornea is oval instead of spherical • Causes blurred vision • Some types can be corrected with lenses
- 43. Diseases of theEye GLAUCOMA • Group of diseases • Affects optic nerve - pressure • Loss of ganglion cells • Gradual loss of sight and eventual blindness • Check eyes regularly • Can be treated
- 44. Diseases of theEye CATARACTS • Clouding forms in lens due to denaturing of lens protein • Obstructs passage of light • Caused by age, chronic exposure to UV, or due to trauma • Removed by surgery
- 45. Vision Correction CONTACT LENSES •Artificial lens placed over cornea • Same as glasses • Corrects for both near and far-sightedness • Also used for cosmetic purposes (eye colour, Hollywood)
- 46. Vision Correction LASIK • “LaserAssisted In Situ Keratomileusis” • Refractive surgery using laser • Corrects near and far- sightedness and astigmatisms