Eyes

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Eyes Vision
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Outermost layer of the Eye

• Cornea window bulges slightly outward,
  allows light to enter only truly transparent
  portion. Absence of blood vessels, abundant pain
  receptors
• Sclera whites of eyes helps with shape of
  eye. Attachment of extrinsic muscles

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Middle layer of the Eye

• Choroid contains blood vessels, and melanin.
  Melanin helps absorb light, reducing amount that
  reflects within eye, increasing visual sharpness
• Ciliary Bodies ring of muscle tissue that holds
  lens in place, functions in shaping lens for
  focusing
• Iris pigmented area regulates amount of light
  thru pupil via smooth muscle fibers

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Innermost layer of the Eye

• Retina contains about ¼ billion receptors 70
  of all sensory receptors in body
• primary cells of retina Photoreceptors rods
  cones
• 125 million rods 6 million cones fovea
• red, blue green

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Fovea

• The center of the macula gives the sharpest
  vision. When we fixate or look directly at an
  object it is imaged on the fovea.

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cells of retina

• Photoreceptors contain retinal pigment bound
  to a protein called opsin 4 types of opsin,
  retinal will absorb a different color wavelength
  depending on the opsin its bound to
• Rods rhodopsin
• Cones red, blue, green colors overlap and
  brain interprets color depending on strength of
  cones stimulation

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cells of retina

• Bipolar cells approx. 6 million begin to
  process info received by photoreceptors
• Between bipolar cells and photoreceptors are
  horizontal cells between bipolar cells and
  ganglion cells are amacrine cells which relay
  or inhibit info laterally across retina and
  between cells
• Ganglion cells axons form optic nerve

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Optic Nerve CN II

• The bundle of over one million nerve fibers that
  carries visual messages from the retina to the
  brain.

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chambers

• Anterior chamber between cornea lens
• Contains aqueous humor produced by capillaries
  of ciliary bodies, exits via Canal of Schlemm,
  replaced every 90min
• . creates pressure, maintains shape,
  nutrients/wastes. Posterior chamber between lens
  retina
• Contains vitreous humor born with. Maintains
  shape of eye

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Normal vision Emmetropia
Emmetropia (normal vision).What is referred to
as normal vision, or emmetropia, happens when
light rays focus precisely on the retina
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Myopia
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Hyperopia
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Astigmatism (ghost vision).Astigmatic people
see with double or ghost vision. Both far and
near objects appear out of focus. This is because
of the uneven diameter of the cornea.
(Oblong-shaped, for instance.) For light rays to
focus precisely on the retina, the cornea usually
needs to be more evenly round.
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presbyopia
Presbyopia (reduced focus-adjusting
ability).Presbyopic people have a reduced
focus-adjusting ability. This results from a loss
of elasticity in the eye's lens, often as part of
the aging process.
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                                       "Isn't it
creepy how they seem to follow you around the
room?"