1. Senses Vision

2. V I S I O N 70% of all receptors in the body are in the eye

3. External Anatomy Eyelids Eyelashes Conjunctiva Lacrimal glands

4. Conjunctiva Inner surface of eyelid

5. Infection: Conjunctivitis “Pink eye”

6. Infection: Conjunctivitis “Pink eye”

7. Lacrimal Glands Lubricate the eye Lysozymes – natural antibiotic Drains into nose

8. Eye Movement 6 muscles / eye 3 Cranial nerves – III Oculomotor – IV Trochlear – VI Abducens

9. Eyeball External Walls “tunics”

10. Outer Sclera White CT “White” of the eye

11. Outer Sclera Central anterior is clear and forms cornea

12. Outer Sclera Cornea can be transplanted – no blood vessels

13. Vascular Tunic Blood-rich for nutrition Lens attaches to anterior end “ciliary body”

14. Sensory Tunic Called - Retina Contains rods and cones Sensory photoreceptors

15. Sensory Tunic Impulses leave by optic nerve No photoreceptors where optic nerve leaves - “blind spot”

17. Rods Gray tones Fx: Dim light & Peripheral vision Loss: Night blindness Usually vitamin A deficiency

18. Cones Color details Heaviest in center of retina – fovea centralis – sharpest vision spot

19. Cones & Colors Blue, Red, & Green More than one type firing – intermediate colors –Red & Blue = Purple

20. Cones & Colors If all 3 firing = white If none firing = black Color interpretation in Brain NOT retina

21. Colorblindness If lack all 3 cones – colorblind – See shades of gray If lack one cone – partial colorblindness

22. Colorblindness Most common is lack of red or green Color vision genes – X chromosome – Sex-linked – Almost always males

23. Lens Focuses light on retina Turns opaque as we age Can lead to cataracts

24. Cataracts

26. Chambers of Eye Liquid (humor) hold shape of eyeball Lens divides into 2 chambers Anterior – aqueous humor Posterior – vitreous humor

27. Chambers of Eye Anterior – aqueous humor – like plasma – nutrients for lens and cornea – Constantly formed and drained

28. Chambers of Eye If drain blocked, increases pressure Glaucoma

29. Chambers of Eye Posterior – vitreous humor – Gel-like protein – Not replaceable

30. Focusing the Eye Lens changes shape to focus image on retina = accommodation

31. Focusing the Eye Myopia – Short vision – Focuses in front of retina – Distant objects appear blurry

32. Focusing the Eye Hyperopia – Far vision – Focuses beyond retina – Close objects appear blurry

33. Focusing the Eye Presbyopia – “Old eye” (40’s) – Lens hardening – Cannot accommodate “near vision” – Hold it out further

34. Focusing the Eye Astigmatism – Unequal curvature of cornea or lens – Focus point different for each eye

35. Visual Nerve Path Retina → Axons → Form bundles of axons → Form Optic Nerve

36. Visual Nerve Path At Optic chiasma – Lateral fibers stay on same side of brain – Medial fibers cross over to other side of brain

37. Visual Nerve Path

38. Lateral and medial fibers form optic tract (left & right)

39. Visual Nerve Path Optic tract synapses with thalamus Form optic radiation on occipital lobe – Visual interpretation