1. Essentials of Human Anatomy & Physiology Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Seventh Edition The Eye & Vision Lecture Slides in PowerPoint by Jerry L. Cook Modified by J. Kalinowski 2-04

2. Slide 8.2 The Eye and Vision Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  70 percent of all sensory receptors are in the eyes - only see 1/6th of eye  Each eye has over a million nerve fibers  Protection for the eye  Most of the eye is enclosed in a bony orbit  A cushion of fat surrounds most of the eye

3. Slide 8.3a Accessory Structures of the Eye Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Eyelids – aka. palpebra  Meets at medial and lateral canthus  Eyelashes Figure 8.1b

4. Slide 8.3b Accessory Structures of the Eye Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Meibomian glands – tarsal glands – modified sebacious glands produce an oily secretion to lubricate the eye  Chalazion - inflammation Figure 8.1b

5. Chalazion

6. Slide 8.3c Accessory Structures of the Eye Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Ciliary glands – modified sweat glands between the eyelashes  Sty - inflammation Figure 8.1b

7. Slide 8.4a Conjunctiva Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Conjunctiva  Membrane that lines the eyelids  Connects to the surface of the eye  Secretes mucus to lubricate the eye  Conjunctivitis – inflammation of – sometimes known as “pink eye”

8. Conjunctivitis

9. Slide 8.4b Accessory Structures of the Eye Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Lacrimal apparatus  Lacrimal gland – produces lacrimal fluid  Lacrimal canals – drains lacrimal fluid from eyes Figure 8.1a

10. Slide 8.4c Accessory Structures of the Eye Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Lacrimal sac – provides passage of lacrimal fluid towards nasal cavity Figure 8.1a

11. Slide 8.4d Accessory Structures of the Eye Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Nasolacrimal duct – empties lacrimal fluid into the nasal cavity Figure 8.1a

12. Slide 8.5 Function of the Lacrimal Apparatus Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Properties of lacrimal fluid  Dilute salt solution (tears)  Contains antibodies and lysozyme  Protects, moistens, and lubricates the eye  Empties into the nasal cavity

13. Slide 8.6 Extrinsic Eye Muscles Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Six eye muscles attach to the outer surface of the eye  Produce gross eye movements  Rectus muscles: lateral, medial, superior, inferior  Oblique muscles: inferior, superior  Need to be able to label on diagram & identify the motions they are responsible for (page 254 of text) Figure 8.2

15. Slide 8.7 Structure of the Eye Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  The wall is composed of three tunics  Fibrous tunic – Outer layer  Vascular tunic (uvea) – middle layer  Sensory tunic – inside layer Figure 8.3a

16. Slide 8.8 The Fibrous Tunic Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Sclera  White connective tissue layer  Seen anteriorly as the “white of the eye”  Cornea  Transparent, central anterior portion  Allows for light to pass through  Repairs itself easily  The only human tissue that can be transplanted without fear of rejection

18. Slide 8.9 Vascular Tunic Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Choroid – posterior portion  Blood-rich nutritive tunic  Dark pigment prevents light from scattering

19. Slide 8.9 Vascular Tunic Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Modified interiorly  Ciliary body – anterior  smooth muscle  Attached to lens  Iris  Pigmented layer that gives eye color  Pupil – rounded opening in the iris for light passage  Circular & radial fibers regulate opening

20. Slide 8.10 Sensory Tunic (Retina) Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Neural layer contains receptor cells (photoreceptors)  Rods & Cones  Signals pass from photoreceptors via a two-neuron chain  Photoreceptors to bipolar neurons  Bipolar neurons to ganglion cells  Signals leave the retina toward the brain through the optic nerve

21. Slide 8.11 Neurons of the Retina Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 8.4

22. Slide 8.12a Neurons of the Retina and Vision Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Rods  Most are found towards the edges of the retina  Allow dim light vision and peripheral vision  Perception is all in gray tones

23. Slide 8.12b Neurons of the Retina and Vision Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Cones  Allow for detailed color vision  Densest in the center of the retina  Fovea centralis  area of the retina with only cones  Area of greatest visual acuity

24. Slide 8.12b Optic disk Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  No photoreceptor cells are at the optic disk, or blind spot  Site of optic nerve leaving eyeball

25. Slide 8.13 Cone Sensitivity Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  There are three types of cones  Different cones are sensitive to different wavelengths  Color blindness is the result of lack of one cone type Figure 8.6

26. Slide 8.14 Lens Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Biconvex crystal-like structure  Held in place by a suspensory ligament attached to the ciliary body Figure 8.3a

27. Slide 8.14 Lens Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Activity of ciliary muscle of ciliary body changes lens thickness to focus light onto retina  Cataracts  Anterior segment – contains watery aqueous humor  Maintains intraocular pressure  Glaucoma  Fluid circulates over eye and is reabsorbed into the blood stream by canal of Schlemm  Posterior segment – contains gel-like vitreous humor Figure 8.3a

29. Internal Eye Chamber Fluids Slide 8.15a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Aqueous humor in Anterior Segment  Watery fluid found in chamber between the lens and cornea  Similar to blood plasma  Helps maintain intraocular pressure  Provides nutrients for the lens and cornea  Reabsorbed into venous blood  Blocked drainage = glaucoma

30. Slide 8.15b Internal Eye Chamber Fluids Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Vitreous humor  Gel-like substance behind the lens  Keeps the eye from collapsing  Lasts a lifetime and is not replaced  Keeps retina firmly against wall of eyeball

31. Vision

32. Light Light must be refracted (bent) so that it focuses on the retina to form an image. The cornea, aqueous humor, & vitreous humor have a constant refractory power The lens is the only refractory structure that can change shape in order to change refractory power.

33. Focus Distance vision is accomplished by: Ciliary muscles relaxation Suspensory ligaments tightening Results in: Maximum flattening of lens (decreased convexity) Decreased refraction

34. Focus Close vision is accomplished by: Ciliary muscles tightening Suspensory ligaments relaxing Results in: Lens rounds up (increased convexity) Increased refraction Requires continuous muscle contractions Prolonged periods of close vision can cause eyestrain

35. Slide 8.16 Lens Accommodation Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  The eye is set for distance vision (over 20 ft away)  The lens must change shape to focus for closer objects  This ability decreases with age Figure 8.9

36. Slide 8.17 Real Image Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Real image is projected on retina:  reversed from left to right  upside down & smaller  Brain adjusts our perception Figure 8.10

37. Correcting the Eye Correct Focus = emmetropia Nearsightedness = myopia Distant objects are blurry (near objects clear) Focus of light in front of retina Eyeball too long lens too strong – too convex Cornea is too curved – too convex Requires concave lens to correct

38. Emmetropia

39. Myopia

40. Correcting the Eye Farsightedness = hyperopia Near objects are blurry – distance objects are clear Focus of light beyond the retina Short eyeball lazy lens – lens too weak – too concave Cornea too flat – too concave Requires convex lens to correct

41. Hyperopia

42. Astigmatism Unequal curvatures in cornea & lens Blurred vision Specially ground lenses required to compensate irregularities

43. Presbyopia Decreasing lens elasticity so lens cannot adjust for close vision Causes difficulty focusing on near objects Typically age related – corrected with reading glasses, etc. Near point of accommodation – closest distance at which you can focus on an object