Physio - Vision

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Physio - Vision
2012-03-12 17:36:26
Physio Vision

Chapter 10
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  1. Fibrous Tunic
    Location - outer layer of eyeball

    Function - give shape to eyeball

    (Composed of sclera, cornea and conjuctiva)
  2. Sclera
    Location - posterior outer layer/white of the eye

    Function - supports and protects eyeball
  3. Cornea
    Location - anterior surface of eyeball

    Function - transmits and refracts light
  4. Vascular Tunic
    Location - middle layer of eyeball

    Function - supplies blood; prevents reflection

    (Composed of choroid, ciliary body and iris/pupil)
  5. Choroid
    Locaton - middle layer in posterior portion of eyeball (lies between sclera and neural layer)

    Function - supplies blood to eyeball

    • -highly pigmented and vascular
    • -absorbs light (prevents it from bouncing around in eye)
  6. Ciliary Body
    Location - anterior portion of vascular tunic

    Function - supports the lens through suspensory ligament and determins its thickness; secretes aqueous humor
  7. Iris
    Location - anterior portion of vascular tunic; continuous with ciliary body

    Function - regulates the diameter of the pupil, and hence the amount of light entering the vitreous chamber

    Controlled by the ANS

    (pupil is hole in iris)

    • (also contains pigment producing cells)
    • -lots = dark brown eyes
    • -less = other colors
  8. Internal Tunic
    Location - inner layer of eyeball

    Function - provides location and support for rods and cones(pigmented epithelium)

    (Composed of retina)
  9. Retina
    Location - principal portion of internal tunic

    Function - photoreception; transmits impulses
  10. Macula Lutea
    Area with very high density in cone cells
  11. Fovea Centralis
    Location - center of macula lutea

    Function - light is focused here
  12. Optic Disk
    Area where no rods or cone cells exist
  13. Lens
    Location - between posterior and vitreous chambers; supported by suspensory ligament of ciliary body

    Function - refracts light and focuses onto fovea centralis
  14. Basic function of eyes
    Eyes are "transducers"
  15. Rods and Cones
    • detect visible light
    • this changes membrane potential
    • sends electrical signals to other retinal neurons
    • ultimately action potentials send to brain
  16. Aqueous Humor
    • fills anterior spaces of eye (anterior to lens)
    • produced by ciliary body
    • nourishes lens and corneal cells
    • constantly produced and drained (via Canal of Schelm)
  17. Vitreous Humor
    • fills posterior spaces of eye (behind the lens)
    • critical function: support retina
  18. Refraction
    Light bends when it passes through different media
  19. Accommodation
    • Ability to change the focus of light on the retina
    • We accommodate by changing the shape of the lens (ciliary body)
  20. Visual Acuity
    Sharpness of vision (ability to distinguish 2 objects at a distance)
  21. Snellen Eye Chart
    Used to test visual acuity

    20/20 - normal vision: you see at 20 ft what a person sees at 20 ft

    20/15 - better than normal: you see at 20 ft what a person sees at 15 ft

    20/30 - worse than normal: you see at 20 ft what a person sees at 30 ft
  22. Emmetropia
    Normal Vision

    Rays focus on retina
  23. Myopia
    • Nearsighted
    • Long eyeball
    • Rays focus in front of retina
    • Concave lenses needed
  24. Hyperopia
    • Farsighted
    • Short eyeball
    • Rays focus behind retina
    • Convex lenses needed
  25. Presbyopia
    • Loss of elasticity
    • Comes with age
    • Reading glasses needed
  26. Astigmatism
    • Uneven lens or distortion in lens
    • Rays do not focus
    • Uneven lens correctd astigmatism