The Eyes and Ears Dr. Jason P. Schwartz PBCC

1. The Eyes and Ears Dr. Jason P. Schwartz PBCC

2. Eye and Associated Structures 70% of all sensory receptors are in the eye 250,000,000 receptors Most of the eye is protected by a cushion of fat and the bony orbit Accessory structures include eyebrows, eyelids, conjunctiva, lacrimal apparatus, and extrinsic eye muscles

4. Palpebrae (Eyelids)

5. If you were to touch the surface of your eye with your finger, * you would be touching the conjunctiva. * * *If you were to touch the surface of your eye with your finger, * you would be touching the conjunctiva. * * *

6. Conjunctiva Covers the inner surface of the eyelids and the anterior surface of the eye. Membrane which produces mucous that lubricates the eye and prevents dryness. Protects the eye. The conjunctiva * covers the inner surface of the eyelids as well as the anterior surface of the eyeball itself. * As a serous membrane, it produces mucous to lubricate the eye and prevent dryness. * It also serves to protect the eye. *The conjunctiva * covers the inner surface of the eyelids as well as the anterior surface of the eyeball itself. * As a serous membrane, it produces mucous to lubricate the eye and prevent dryness. * It also serves to protect the eye. *

7. Conjunctiva Transparent membrane that: Lines the eyelids as the palpebral conjunctiva Covers the whites of the eyes as the ocular conjunctiva Lubricates and protects the eye

8. Conjunctivitis Inflammation of the conjunctiva by: Bacteria, fungi or viruses Trauma Conjunctivitis * is inflammation of the outer covering of the cornea (conjunctiva). * The most common causes of conjunctivitis include * infection by bacteria, fungi or viruses, and * trauma. * *Conjunctivitis * is inflammation of the outer covering of the cornea (conjunctiva). * The most common causes of conjunctivitis include * infection by bacteria, fungi or viruses, and * trauma. * *

9. Conjunctivitis

10. Conjunctivitis (viral)

11. Conjunctivitis (Bacterial)

12. Lacrimal Apparatus Consists of the lacrimal gland and associated ducts Lacrimal glands secrete tears Tears Contain mucus, antibodies, and lysozyme

13. Three Types of Tears  Basal tears: The cornea is continually kept moist and nourished by basal tears. They lubricate the eye and help to keep it clear of dust. Reflex tears: The second type of tears are used when the eye gets irritated by foreign particles, or substances such as onion vapors, tear gas or pepper spray. These reflex tears attempt to wash out irritants that may have come into contact with the eye. �Crying or weeping (Physic tears): The third type, referred to as crying or weeping or physic, is increased lacrimation due to strong emotional stress, depression or physical pain. Tears brought about by emotions have a different chemical make up than those for lubrication.

14. Lacrimal Apparatus

15. Structure of the Eyeball

16. The eye is made up of three tunics or layers of material. * The outermost tunic is called the fibrous tunic. The fibrous tunic is made up of the opaque white sclera * which is the tough layer which covers most of the eye and is seen anteriorly as the white of the eye, * and the transparent cornea in the front. *The eye is made up of three tunics or layers of material. * The outermost tunic is called the fibrous tunic. The fibrous tunic is made up of the opaque white sclera * which is the tough layer which covers most of the eye and is seen anteriorly as the white of the eye, * and the transparent cornea in the front. *

17. Fibrous Tunic Sclera Functions: Protects eye Shapes eye Anchors eye muscles Cornea Functions: Transparent window for light entry Refracts light The sclera: * * protects the inner structures of the eye, * gives the eye its shape, and * provides a tough surface to which the tendons from the muscles which move the eye may be anchored. * The cornea * * serves as a transparent window which bulges forward from the place where it joins the sclera to allow light to enter the eye. As the light travels through the cornea it is refracted (bent) * so the image may be directed to the area of the eye where the receptors are located. *The sclera: * * protects the inner structures of the eye, * gives the eye its shape, and * provides a tough surface to which the tendons from the muscles which move the eye may be anchored. * The cornea * * serves as a transparent window which bulges forward from the place where it joins the sclera to allow light to enter the eye. As the light travels through the cornea it is refracted (bent) * so the image may be directed to the area of the eye where the receptors are located. *

18. Fig. 16.23

19. The middle tunic or layer is the vascular tunic or uvea which is pigmented. * Structures which make up the vascular tunic include: * the posterior choroid, * the ciliary body *, and * the anterior iris. *The middle tunic or layer is the vascular tunic or uvea which is pigmented. * Structures which make up the vascular tunic include: * the posterior choroid, * the ciliary body *, and * the anterior iris. *

20. Vascular Tunic Choroid Functions: Provides nutrients to all eye tunics. Absorbs light preventing reflecting & scattering of light within the eye. Ciliary Body Functions: Ciliary processes secrete aqueous humor. Suspensory ligaments hold lens in place. Ciliary muscles pull on the ligaments to change the thickness of the lens. The choroid is darkly pigmented and highly vascular. Its functions include: * providing O2 and nutrients to the three tunics of the eye, * absorbing light to prevent its reflection and scattering within the eye. * The ciliary body is a circular ring of tissue that encircles the lens. It * secretes a watery fluid within the eye called the aqueous humor and * anchors the suspensory ligaments which hold the lens in place. The * ciliary muscles, to which the suspensory ligaments attach, help to change the thickness of the lens by pulling on the ligaments. * The iris * is the visible colored part of the eye which constricts or dilates to adjust the amount of light that can enter the eye. *The choroid is darkly pigmented and highly vascular. Its functions include: * providing O2 and nutrients to the three tunics of the eye, * absorbing light to prevent its reflection and scattering within the eye. * The ciliary body is a circular ring of tissue that encircles the lens. It * secretes a watery fluid within the eye called the aqueous humor and * anchors the suspensory ligaments which hold the lens in place. The * ciliary muscles, to which the suspensory ligaments attach, help to change the thickness of the lens by pulling on the ligaments. * The iris * is the visible colored part of the eye which constricts or dilates to adjust the amount of light that can enter the eye. *

21. The ciliary muscles * * form the largest part of the ciliary body. They form a muscular ring around the inside of the ciliary body which contracts or relaxes to change the tension on the suspensory ligaments which hold the lens in place. * Changes in tension on the the suspensory ligaments changes the thickness of the lens. The ciliary processes * * are also a part of the ciliary body. They contain capillaries which secrete the fluid that fills the anterior part of the eye. * The ciliary muscles * * form the largest part of the ciliary body. They form a muscular ring around the inside of the ciliary body which contracts or relaxes to change the tension on the suspensory ligaments which hold the lens in place. * Changes in tension on the the suspensory ligaments changes the thickness of the lens. The ciliary processes * * are also a part of the ciliary body. They contain capillaries which secrete the fluid that fills the anterior part of the eye. *

22. The aqueous humor secreted by the ciliary processes * circulates in the area of the eye anterior to the lens as well as diffusing through the material which fills the inside of the eye behind the lens. The area which is filled with aqueous humor is referred to as the anterior segment of the eye, * and is divided into an anterior chamber in front of the iris and a posterior chamber where the lens is located. * As the production of aqueous humor is a continuous process, aqueous humor must be able to leave the eye at a rate equivalent to its production so that the pressure inside the eye remains the same. The aqueous humor leaves the eye and moves into the venous blood by flowing into the canal of Schlemm (scleral venous sinus) * which circles the eye at the junction between the sclera and the cornea. *The aqueous humor secreted by the ciliary processes * circulates in the area of the eye anterior to the lens as well as diffusing through the material which fills the inside of the eye behind the lens. The area which is filled with aqueous humor is referred to as the anterior segment of the eye, * and is divided into an anterior chamber in front of the iris and a posterior chamber where the lens is located. * As the production of aqueous humor is a continuous process, aqueous humor must be able to leave the eye at a rate equivalent to its production so that the pressure inside the eye remains the same. The aqueous humor leaves the eye and moves into the venous blood by flowing into the canal of Schlemm (scleral venous sinus) * which circles the eye at the junction between the sclera and the cornea. *

23. Aqueous Humor Helps support the eye internally due to the intraocular pressure it produces inside the eye. Supplies nutrients & oxygen to the cornea, lens and portions of the retina. Carries away metabolic wastes from the cornea, lens and portions of the retina. The aqueous humor: * helps support the eye internally due to the intraocular pressure it produces inside the eye, * supplies nutrients and O2 to the avascular cornea, lens and to parts of the retina and * carries off metabolic wastes produced by the cornea, lens and other structures inside the eye. *The aqueous humor: * helps support the eye internally due to the intraocular pressure it produces inside the eye, * supplies nutrients and O2 to the avascular cornea, lens and to parts of the retina and * carries off metabolic wastes produced by the cornea, lens and other structures inside the eye. *

24. You are looking at an anterior view of the iris, the colored part of the eye that you can see from the outside of the eye. * The function of the iris is to constrict or dilate to adjust the size of the pupil which is the opening in the center of the iris. * Light must pass through the pupil to enter the posterior segment of the eye where the receptors are located. * The size of the pupil, determines how much light can enter the eye. *You are looking at an anterior view of the iris, the colored part of the eye that you can see from the outside of the eye. * The function of the iris is to constrict or dilate to adjust the size of the pupil which is the opening in the center of the iris. * Light must pass through the pupil to enter the posterior segment of the eye where the receptors are located. * The size of the pupil, determines how much light can enter the eye. *

26. Anterior Segment

28. The posterior segment * of the eye is the area behind the lens. The posterior segment is filled with a jelly-like substance, the vitreous humor. *The posterior segment * of the eye is the area behind the lens. The posterior segment is filled with a jelly-like substance, the vitreous humor. *

29. Vitreous Humor Transmits light within the posterior segment. Supports the lens posteriorly. Holds the retina in place. Contributes to intraocular pressure. The vitreous humor * conducts light within the posterior segment, * supports the lens posteriorly, * holds the retina in place, and * along with aqueous humor, contributes to intraocular pressure within the eye. *The vitreous humor * conducts light within the posterior segment, * supports the lens posteriorly, * holds the retina in place, and * along with aqueous humor, contributes to intraocular pressure within the eye. *

30. The third, or innermost tunic making up the eye is an outpocketing of the brain referred to as the sensory tunic. * The specific name given to the sensory tunic is the retina. * The retina is actually composed of two separate layers. *The third, or innermost tunic making up the eye is an outpocketing of the brain referred to as the sensory tunic. * The specific name given to the sensory tunic is the retina. * The retina is actually composed of two separate layers. *

31. Retina Pigmented Layer Absorbs light Carries out phagocytosis Stores Vitamin A Neural Layer Contains photoreceptors (rods and cones) for visual perception Contains bipolar cells & ganglion cells for visual impulse transmission The outermost pigmented layer of the retina lies adjacent to the choroid. It functions to: * absorb light so it will not be reflected within the eye, * carry out phagocytosis to remove cellular debris and other materials which might interfere with vision, and * store vitamin A. * The transparent inner layer of the retina is referred to as the neural layer. * Only the neural layer contains the photoreceptors that respond to light, * the bipolar cells and ganglion cells *which process visual stimuli and conduct nerve inpulses to the brain. * The outermost pigmented layer of the retina lies adjacent to the choroid. It functions to: * absorb light so it will not be reflected within the eye, * carry out phagocytosis to remove cellular debris and other materials which might interfere with vision, and * store vitamin A. * The transparent inner layer of the retina is referred to as the neural layer. * Only the neural layer contains the photoreceptors that respond to light, * the bipolar cells and ganglion cells *which process visual stimuli and conduct nerve inpulses to the brain. *

32. Retina Fovea Centralis Contains only closely packed cones Provides acute color vision in bright light Macula Lutea Contains more widely spaced cones Other areas of Retina Contain only rods Provide night, dim light & peripheral vision Shades of grey only Optic Disc Contains no receptors Blind spot As the fovea centralis * contains the highest concentration of closely packed cones, * it provides the sharpest color images in bright light. * The macula lutea * also contains cones, but they are more widely spaced and are interspersed with rods. * As a result, the images produced by the macula lutea are not as sharp and clear as those produced by the fovea centralis. * Other areas of the retina besides the fovea centralis and the macula lutea only contain rods. * Because rods are very sensitive to bright light, they only function at night, in dim light situations or in peripheral vision. * Images produced by rods are somewhat blury and are only in shades of grey rather than in other colors. * As indicated previously, the optic disc * contains neither rods nor cones, and is therefore unable to respond to visual stimuli. * For this reason, it is referred to as the blind spot of the eye. *As the fovea centralis * contains the highest concentration of closely packed cones, * it provides the sharpest color images in bright light. * The macula lutea * also contains cones, but they are more widely spaced and are interspersed with rods. * As a result, the images produced by the macula lutea are not as sharp and clear as those produced by the fovea centralis. * Other areas of the retina besides the fovea centralis and the macula lutea only contain rods. * Because rods are very sensitive to bright light, they only function at night, in dim light situations or in peripheral vision. * Images produced by rods are somewhat blury and are only in shades of grey rather than in other colors. * As indicated previously, the optic disc * contains neither rods nor cones, and is therefore unable to respond to visual stimuli. * For this reason, it is referred to as the blind spot of the eye. *

33. Retina This is a view of the retina from the front of the eye. The macula lutea * surrounds the fovea centralis * directly behind the pupil through which light enters the posterior segment of the eye. The optic disc * * is on the left where the blood vessels and nerves exit the eye. *This is a view of the retina from the front of the eye. The macula lutea * surrounds the fovea centralis * directly behind the pupil through which light enters the posterior segment of the eye. The optic disc * * is on the left where the blood vessels and nerves exit the eye. *

34. The Retina: Photoreceptors - 250,000,000 Rods: Respond to dim light Are used for peripheral vision Cones: Respond to bright light Have high-acuity color vision Are found in the macula lutea Are concentrated in the fovea centralis

35. Photoreceptors Notice the specific arrangement of cells in the fovea centralis. * Each cone * synapses with a single bipolar cell, * which synapses with a single ganglion cell * which sends information along its axon to the optic nerve. *Notice the specific arrangement of cells in the fovea centralis. * Each cone * synapses with a single bipolar cell, * which synapses with a single ganglion cell * which sends information along its axon to the optic nerve. *

36. Cones Are located in macula lutea but are most highly concentrated in the fovea centralis. Are sensitive to bright light (daylight) situations in which light is very intense. Each cone synapses with a single bipolar cell which synapses with a single ganglion cell. The axons of ganglion cells form the optic nerve to conduct visual images to the brain. Provide acute (sharp) color images (vision). While cones are found scattered throughout the macula lutea, they are most highly concentrated in the fovea centralis. * They respond to bright visual stimuli such as one would encounter during daylight or to bright lights at other times. * Each cone synapses with a single bipolar cell which in turn synapses with a single ganglion cell. * The axons of the ganglion cells form the optic nerve which carries visual images from each cone to the brain. * Thus the visual stimuli sent to the brain from the cones sharp and in color. *While cones are found scattered throughout the macula lutea, they are most highly concentrated in the fovea centralis. * They respond to bright visual stimuli such as one would encounter during daylight or to bright lights at other times. * Each cone synapses with a single bipolar cell which in turn synapses with a single ganglion cell. * The axons of the ganglion cells form the optic nerve which carries visual images from each cone to the brain. * Thus the visual stimuli sent to the brain from the cones sharp and in color. *

37. Cones There are three different types of cones. One type only responds to wavelengths of light which are found in the green area of the visible light spectrum.* These are called green cones. Another type of cone responds only to wavelengths of light in the red area of the visible light spectrum. These are the red cones. * Finally there are blue cones which respond only to the blue wavelengths of the spectrum. * As the brain receives visual stimuli from these colored receptors, the brain processes them to give us images in all the various colors. *There are three different types of cones. One type only responds to wavelengths of light which are found in the green area of the visible light spectrum.* These are called green cones. Another type of cone responds only to wavelengths of light in the red area of the visible light spectrum. These are the red cones. * Finally there are blue cones which respond only to the blue wavelengths of the spectrum. * As the brain receives visual stimuli from these colored receptors, the brain processes them to give us images in all the various colors. *

38. Photoreceptors Rods are primarily found in the retina, outside of the fovea centralis. Although there are some rods scattered among the cones in the outer parts of the macula lutea, most of our vision from rods comes from other areas of the retina. * Images from rods are not as sharp as those from cones because of their arrangement with bipolar and ganglion cells. Notice from the diagram that several rods synapse with one or more bipolar cells. * * Thus the information received by the bipolar cells from rods may include stimuli from several rods. * More than one bipolar cell may synapse with a single ganglion cell, * which sends the information from many rods to the brain. *Rods are primarily found in the retina, outside of the fovea centralis. Although there are some rods scattered among the cones in the outer parts of the macula lutea, most of our vision from rods comes from other areas of the retina. * Images from rods are not as sharp as those from cones because of their arrangement with bipolar and ganglion cells. Notice from the diagram that several rods synapse with one or more bipolar cells. * * Thus the information received by the bipolar cells from rods may include stimuli from several rods. * More than one bipolar cell may synapse with a single ganglion cell, * which sends the information from many rods to the brain. *

39. Rods Most highly concentrated in the retina outside the macula lutea Many rods synapse with a single bipolar cell Many bipolar cells may synapse with a single ganglion cell which carries stimuli to brain More sensitive & function only in dim light, night and peripheral vision Images are blurry and only in shades of gray Rods * are most highly concentrated in the retina outside of the macula lutea. * Several rods may synapse with a single bipolar cell. More than one bipolar cell * may synapse with a single ganglion cell which carries the information to the brain along its axon. * Rods are much more sensitive to light than cones. * As a result, in daylight and bright light situations, the rods are overwhelmed and are thus inactivated. For these reasons, the rods only function effectively at night, in dim light situations and in peripheral vision. * The images from rods are fuzzy and are only in shades of gray. Thus night vision is not colored. * Rods * are most highly concentrated in the retina outside of the macula lutea. * Several rods may synapse with a single bipolar cell. More than one bipolar cell * may synapse with a single ganglion cell which carries the information to the brain along its axon. * Rods are much more sensitive to light than cones. * As a result, in daylight and bright light situations, the rods are overwhelmed and are thus inactivated. For these reasons, the rods only function effectively at night, in dim light situations and in peripheral vision. * The images from rods are fuzzy and are only in shades of gray. Thus night vision is not colored. *

40. Lens Refracts (bends) light Focuses precise image on the retina (fovea) through accommodation (changing thickness) The lens is a transparent, flexible, biconcave structure which is held in place by the suspensory ligaments. * Its primary job is to refract light passing through it so that an image may be focused on the fovea centralis. * Because the lens is flexible, tension exerted by the ciliary muscles through the suspensory ligaments changes the thickness of the lens. * This adjustment in the thickness of the lens to focus images precisely on the fovea is called accommodation.The lens is a transparent, flexible, biconcave structure which is held in place by the suspensory ligaments. * Its primary job is to refract light passing through it so that an image may be focused on the fovea centralis. * Because the lens is flexible, tension exerted by the ciliary muscles through the suspensory ligaments changes the thickness of the lens. * This adjustment in the thickness of the lens to focus images precisely on the fovea is called accommodation.

41. Myopia (Nearsighted) Eyeball too long Distant objects focused in front of retina Image striking retina is blurred Myopia * is a condition where the eyeball is longer than normal. As a result, the image is focused in front of the fovea rather than directly on it. * Thus the actual image striking the fovea is not in sharp focus. * * Individuals who are near sighted can see nearby objects clearly because the lens can accommodate sufficiently to adjust the focal point. That is not the case for things farther away. * This condition may be corrected by using glasses which have concave lenses* which are ground precisely to correct the problem. * The condition may also be corrected by laser surgery which flattens the cornea to adjust the focal point for distant objects. * Myopia * is a condition where the eyeball is longer than normal. As a result, the image is focused in front of the fovea rather than directly on it. * Thus the actual image striking the fovea is not in sharp focus. * * Individuals who are near sighted can see nearby objects clearly because the lens can accommodate sufficiently to adjust the focal point. That is not the case for things farther away. * This condition may be corrected by using glasses which have concave lenses* which are ground precisely to correct the problem. * The condition may also be corrected by laser surgery which flattens the cornea to adjust the focal point for distant objects. *

42. Hyperopia (Farsighted) Eyeball too short, lens too thin or too stiff. Nearby objects are focused behind retina. Image striking the fovea is blurred. Hyperopia or farsightedness * is due to the eye being too short, the lens too thin, or the lens being too stiff to focus the image precisely on the fovea. * As a result, the image of a nearby object is focused behind the fovea * causing the image striking the fovea to be blurry. * * Farsighted individuals can see distant objects clearly. This condition * may be corrected by using a convex lens * to bring the image of nearby objects forward far enough * for the image to be focused precisely on the fovea. *Hyperopia or farsightedness * is due to the eye being too short, the lens too thin, or the lens being too stiff to focus the image precisely on the fovea. * As a result, the image of a nearby object is focused behind the fovea * causing the image striking the fovea to be blurry. * * Farsighted individuals can see distant objects clearly. This condition * may be corrected by using a convex lens * to bring the image of nearby objects forward far enough * for the image to be focused precisely on the fovea. *

43. Problems of Refraction

44. Extrinsic Eye Muscles Six straplike extrinsic eye muscles Enable the eye to follow moving objects Maintain the shape of the eyeball

45. Fig. 16.22c

46. Extrinsic Eye Muscles

48. Summary of Cranial Nerves and Muscle Actions Names, actions, and cranial nerve innervation of the extrinsic eye muscles

49. The Retina: the Optic Disc The optic disc: Is the site where the optic nerve leaves the eye Lacks photoreceptors (the blind spot) Other than the optic disc, the only point where the retina is attached to the rest of the eyeball is an anterior ring called the ora serrata.

52. Ophthalmoscope

53. Eye with Glaucoma

54. Hypertension

55. Diabetes and the Retina

57. Focusing for Close Vision Close vision requires: Accommodation � changing the lens shape by ciliary muscles to increase refractory power Constriction � the pupillary reflex constricts the pupils to prevent divergent light rays from entering the eye Convergence � medial rotation of the eyeballs toward the object being viewed (medial rectus muscles)

58. Focusing for Close Vision

59. Fig. 16.30b

60. Presbyopia

61. Problems of Refraction Emmetropic eye � normal eye with light focused properly Myopic eye (nearsighted) � the focal point is in front of the retina Corrected with a concave lens Hyperopic eye (farsighted) � the focal point is behind the retina Corrected with a convex lens

63. The computer-controlled laser removes the tissue under the flap and reshapes the cornea of the affected eye. In less than 60 seconds, ultraviolet light and high-energy pulses from the laser reshape the internal cornea (the stroma). LASIK EYE SURGERY

64. Cararact Clouding of lens due to aging, diabetes mellitus, heavy smoking, frequent exposure to intense sunlight or congenital factors To refract light and focus sharp images on the fovea, the lens must be transparent. * The lens may become cloudy or opaque as a result of aging, diabetes mellitus, heavy smoking, frequent exposure to bright sunlight or congenital factors. * If the light cannot pass through all parts of the lens, the image may be dim and unfocused. * Treatment for cataracts * involves the replacement of the lens. *To refract light and focus sharp images on the fovea, the lens must be transparent. * The lens may become cloudy or opaque as a result of aging, diabetes mellitus, heavy smoking, frequent exposure to bright sunlight or congenital factors. * If the light cannot pass through all parts of the lens, the image may be dim and unfocused. * Treatment for cataracts * involves the replacement of the lens. *

65. Cataracts Eye without a cataract Eye with a cataract

66. Cataract Extraction (1)

67. Cataract Extraction (2)

68. Cataract Extraction (3)

69. Glaucoma Most common cause of blindness. Increasing intraocular pressure compresses retina, optic nerve & blood vessels. Late symptoms include blurred vision & halos around bright objects Glaucoma * is the most common cause of blindness in the U.S. It is caused by increasing intraoccular pressure inside the eye, * which compresses the retina, optic nerve and the blood vessels that supply blood to the eye, shutting off the supply of nutrients. Although glaucoma may develop rapidly, * late symptoms may include blurred vision and halos around bright objects. * Aqueous humor * is constantly being produced by the ciliary processes within the eye. As long as an equivalent amount of aqueous humor can drain from the anterior segment through the mesh network at the junction between the cornea and the sclera * and into the canal of Schlemn, * the intraocular pressure remains constant. * However, if the aqueous humor drains more slowly than it is produced, pressure builds up within the eye gradually reducing the flow of blood and nutrients. Open angle glaucoma * is caused by the aqueous humor draining too slowly. * In angle closure glaucoma, there is such a sharp angle between the iris and the mesh network through which the aqueous humor must drain to reach the canal of Schlemn that the aqueous humor cannot drain due to the iris being pressed against and covering the area the drainage must occur through. * * Glaucoma * is the most common cause of blindness in the U.S. It is caused by increasing intraoccular pressure inside the eye, * which compresses the retina, optic nerve and the blood vessels that supply blood to the eye, shutting off the supply of nutrients. Although glaucoma may develop rapidly, * late symptoms may include blurred vision and halos around bright objects. * Aqueous humor * is constantly being produced by the ciliary processes within the eye. As long as an equivalent amount of aqueous humor can drain from the anterior segment through the mesh network at the junction between the cornea and the sclera * and into the canal of Schlemn, * the intraocular pressure remains constant. * However, if the aqueous humor drains more slowly than it is produced, pressure builds up within the eye gradually reducing the flow of blood and nutrients. Open angle glaucoma * is caused by the aqueous humor draining too slowly. * In angle closure glaucoma, there is such a sharp angle between the iris and the mesh network through which the aqueous humor must drain to reach the canal of Schlemn that the aqueous humor cannot drain due to the iris being pressed against and covering the area the drainage must occur through. * *

70. Glaucoma The top figure shows the optic disc in a normal eye. * The bottom figure shows the effect of increased intraoccular pressure on the optic disc caused by glaucoma. *The top figure shows the optic disc in a normal eye. * The bottom figure shows the effect of increased intraoccular pressure on the optic disc caused by glaucoma. *

71. Glaucoma

72. Blind, painful left eye due to advanced, congenital glaucoma

73. Macular Degeneration Most common cause of vision loss after 65. Progressive deterioration of macula causing loss of central vision Degeneration of the macula lutea * is the most common cause of vision loss after the age of 65. * It is due to progressive deterioration of the macula. * Since the images of things we look directly at are focused on the macula and the fovea centralis, * deterioration of the macula affects the quality of images in the central area of our vision. * Here you can see that the center of the image is not as sharp and distinct as the peripheral areas. This is typical of macular degeneration. Macular degeneration typically occurs in two primary forms. * The first is called the dry form, and is due to an over accumulation of debris from visual pigments which have reacted to light in cones. Normally the pigmented layer of the retina would remove these by phagocytosis. However, if the build up of debris occurs too rapidly, the pigmented cells will not be able to remove the debris fast enough and degeneration of the macula will occur. * The second type of macular degeneration is caused by invasion of the macula with new blood vessels from the choroid. This causes scarring of the macula and may result in separation of the pigmented and neural layers of the retina. This separation is called retinal detachment. *Degeneration of the macula lutea * is the most common cause of vision loss after the age of 65. * It is due to progressive deterioration of the macula. * Since the images of things we look directly at are focused on the macula and the fovea centralis, * deterioration of the macula affects the quality of images in the central area of our vision. * Here you can see that the center of the image is not as sharp and distinct as the peripheral areas. This is typical of macular degeneration. Macular degeneration typically occurs in two primary forms. * The first is called the dry form, and is due to an over accumulation of debris from visual pigments which have reacted to light in cones. Normally the pigmented layer of the retina would remove these by phagocytosis. However, if the build up of debris occurs too rapidly, the pigmented cells will not be able to remove the debris fast enough and degeneration of the macula will occur. * The second type of macular degeneration is caused by invasion of the macula with new blood vessels from the choroid. This causes scarring of the macula and may result in separation of the pigmented and neural layers of the retina. This separation is called retinal detachment. *

75. Light

76. Color Blindness Congenital lack of one or more cone types Deficit or absence of red or green cones most common Sex-linked trait (8-12% of population) Most common in males Colorblindness * is due to a congenital lack of one or more cone types. * The most common type of colorblindness is red-green, due to the lack of cones sensitive to red or green wavelengths of light. * This is a sex-linked trait which is carried on the X chromosomes. * Since males inherit only one X chromosome, the condition occurs most commonly in males. * Look at the three figures shown. * What numbers can you see in each of these? Charts like this are used to determine if a person has the cones which are necessary to distinguish the colors used to form the numbers. *Colorblindness * is due to a congenital lack of one or more cone types. * The most common type of colorblindness is red-green, due to the lack of cones sensitive to red or green wavelengths of light. * This is a sex-linked trait which is carried on the X chromosomes. * Since males inherit only one X chromosome, the condition occurs most commonly in males. * Look at the three figures shown. * What numbers can you see in each of these? Charts like this are used to determine if a person has the cones which are necessary to distinguish the colors used to form the numbers. *

82. The next objective requires you to be able to identify the structures of the ear from a diagram and indicate their functions. * The ear is divided functionally into three areas: * the external ear, * the middle ear, and * the internal ear. *The next objective requires you to be able to identify the structures of the ear from a diagram and indicate their functions. * The ear is divided functionally into three areas: * the external ear, * the middle ear, and * the internal ear. *

83. The primary structures associated with the external ear include the following structures. * Theauricle or pinna, collects sound waves and channels them into the second structure, * the external auditory canal. The external auditory canal directs the sound waves to the tympanum (ear drum) * which separates the external ear from the middle ear. *The primary structures associated with the external ear include the following structures. * Theauricle or pinna, collects sound waves and channels them into the second structure, * the external auditory canal. The external auditory canal directs the sound waves to the tympanum (ear drum) * which separates the external ear from the middle ear. *

84. Middle Ear As sound waves strike the tympanic membrane, it vibrates. Attached to the tympanic membrane and spanning the middle ear is a series of three small bones which are referred to as ossicles. * The first middle ear ossicle, called the malleus, * is connected directly to the tympanic membrane. Vibrations of the tympanic membrane are conducted to the malleus. The malleus is connected to the second ossicle, the incus. * Vibrations of the malleus are conducted to the incus. The incus connects to the third ossicle, the stapes. * Vibrations of the incus areconducted to the stapes. The stapes is connected to a membranous structure called the oval window, * which conducts vibrations from the incus into the inner ear. The three middle ear ossicles work together to conduct sound from the tympanic membrane through the middle ear into the inner ear through the oval window. * The pharyngotympanic or eustachian tube connects the middle ear with the pharynx. Its function is to equalize the pressure inside the middle ear with the atmospheric pressure being exerted against the tympanic membrane. If it were not for the pressure equalizing effect of the eustachian tubes, the tympanic membranes might rupture if pressure differences were to become too great. The �popping� of ones ears occurs when air flows through the eustachian tubes to equalize the pressure as altitude changes are experienced. *As sound waves strike the tympanic membrane, it vibrates. Attached to the tympanic membrane and spanning the middle ear is a series of three small bones which are referred to as ossicles. * The first middle ear ossicle, called the malleus, * is connected directly to the tympanic membrane. Vibrations of the tympanic membrane are conducted to the malleus. The malleus is connected to the second ossicle, the incus. * Vibrations of the malleus are conducted to the incus. The incus connects to the third ossicle, the stapes. * Vibrations of the incus areconducted to the stapes. The stapes is connected to a membranous structure called the oval window, * which conducts vibrations from the incus into the inner ear. The three middle ear ossicles work together to conduct sound from the tympanic membrane through the middle ear into the inner ear through the oval window. * The pharyngotympanic or eustachian tube connects the middle ear with the pharynx. Its function is to equalize the pressure inside the middle ear with the atmospheric pressure being exerted against the tympanic membrane. If it were not for the pressure equalizing effect of the eustachian tubes, the tympanic membranes might rupture if pressure differences were to become too great. The �popping� of ones ears occurs when air flows through the eustachian tubes to equalize the pressure as altitude changes are experienced. *

85. Middle Ear In this view of the middle ear ossicles, you can see that they are suspended by ligaments connected to bones and tendons which are connected to muscles. The muscles provide a means to dampen the movement of the middle ear ossicles during violent or intense sound to reduce damage to the ossicles. *In this view of the middle ear ossicles, you can see that they are suspended by ligaments connected to bones and tendons which are connected to muscles. The muscles provide a means to dampen the movement of the middle ear ossicles during violent or intense sound to reduce damage to the ossicles. *

86. Ear Ossicles The tympanic cavity contains three small bones: the malleus, incus, and stapes Transmit vibratory motion of the eardrum to the oval window

88. Inner Ear Bony labyrinth Tortuous channels worming their way through the temporal bone Contains the vestibule, the cochlea, and the semicircular canals Filled with perilymph

89. Inner Ear The inner ear is sometimes referred to as the �labyrinth� because of its shape. It lies deep within the temporal bone. The bony labyrinth is a system of channels in the bone which are filled with fluid similar to cerebral spinal fluid. The inner ear has three functional parts: the semicircular canals (#1, 7 & 8 above), the cochlea (5 & 6 above) and * the vestibule * which is the central area enclosed by the square. *The inner ear is sometimes referred to as the �labyrinth� because of its shape. It lies deep within the temporal bone. The bony labyrinth is a system of channels in the bone which are filled with fluid similar to cerebral spinal fluid. The inner ear has three functional parts: the semicircular canals (#1, 7 & 8 above), the cochlea (5 & 6 above) and * the vestibule * which is the central area enclosed by the square. *

90. Vestibule Suspended in the fluid inside the bony labyrinth of the inner ear is a continuous system of membranous sacks and ducts. This membranous labyrinth is filled with fluids which are similar to intracellular fluids inside cells. * The vestibule contains a membranous sack called the Utricle, * which continues into the semicircular canals forming the membranous labyrinth in that area. It houses sensory receptors which are associated with perception of dynamic equilibrium. Another membranous sack in the vestibule, * the Saccule, * continues into the cochlea forming the cochlear duct which houses the receptors that are sensitive to sound . Vibrations of the oval window (# 10), are conducted through the fluid in the bony labyrinth and membranous labyrinth throughout the inner ear. *Suspended in the fluid inside the bony labyrinth of the inner ear is a continuous system of membranous sacks and ducts. This membranous labyrinth is filled with fluids which are similar to intracellular fluids inside cells. * The vestibule contains a membranous sack called the Utricle, * which continues into the semicircular canals forming the membranous labyrinth in that area. It houses sensory receptors which are associated with perception of dynamic equilibrium. Another membranous sack in the vestibule, * the Saccule, * continues into the cochlea forming the cochlear duct which houses the receptors that are sensitive to sound . Vibrations of the oval window (# 10), are conducted through the fluid in the bony labyrinth and membranous labyrinth throughout the inner ear. *

91. Maculae Monitors position of head in space Responds to straight-line changes in speed & direction Receptors for static equilibrium The utricle and the saccule in the vestibule of each ear contain receptors called a macula. * * These monitor the position of the head in space * and respond to linear acceleration forces. * Thus the maculae serve as receptors for static equilibrium or our posture and straight line movements in space. * The utricle and the saccule in the vestibule of each ear contain receptors called a macula. * * These monitor the position of the head in space * and respond to linear acceleration forces. * Thus the maculae serve as receptors for static equilibrium or our posture and straight line movements in space. *

95. Inner Ear As indicated previously, the membranous utricle extends from the vestibule through each of the semicircular canals. * At the base of each semicircular canal is an expanded area, the ampulla, which contains receptors for rotational movements. * As indicated previously, the membranous utricle extends from the vestibule through each of the semicircular canals. * At the base of each semicircular canal is an expanded area, the ampulla, which contains receptors for rotational movements. *

99. Inner Ear As indicated previously, vibrations of the stapes against the oval window * transmit sound waves into the fluids of the inner ear. * *As indicated previously, vibrations of the stapes against the oval window * transmit sound waves into the fluids of the inner ear. * *

100. Inner Ear From the vestibule, the waves pass through the fluid into the cochlea * * where the receptors for sound are located. *From the vestibule, the waves pass through the fluid into the cochlea * * where the receptors for sound are located. *

101. Cochlea Unrolled In this illustration of the inner ear, the cochlea has been unrolled to show the relationship between the structures we have been discussing more clearly. * Vibrations of the stapes * are transmitted through the oval window, * into the fluids of the vestibule, * and on into the upper scala vestibuli duct inside the cochlea. * Depending on their frequency, the sound waves eventually pass through the cochlear duct * and the spiral organ of Corti * which sends impulses to the brain. Having passed through the cochlear duct into the scala tympani, * the sound waves travel on to the round window * which acts as a relief valve, allowing the vibrations to dissipate into the air filled middle ear. *In this illustration of the inner ear, the cochlea has been unrolled to show the relationship between the structures we have been discussing more clearly. * Vibrations of the stapes * are transmitted through the oval window, * into the fluids of the vestibule, * and on into the upper scala vestibuli duct inside the cochlea. * Depending on their frequency, the sound waves eventually pass through the cochlear duct * and the spiral organ of Corti * which sends impulses to the brain. Having passed through the cochlear duct into the scala tympani, * the sound waves travel on to the round window * which acts as a relief valve, allowing the vibrations to dissipate into the air filled middle ear. *

102. Spiral Organ of Corti Receptor organ of hearing Different frequencies of vibrations (compression waves) in cochlea stimulate different areas of Organ of Corti Interpreted as differences in pitch This cross section of the cochlea shows the path the fluid vibrations will take in traveling from the upper scala vestibuli duct, through the cochlear duct and through the spiral organ of Corti. * The spiral organ of Corti contains the receptors for hearing. * Different frequencies of sound pass through the organ of Corti at different places along the cochlea which are stimulated and initiate impulses. * The impulses from the different areas of the spiral organ of Corti are interpreted by the brain as differences in pitch. * The vestibulocochlear nerve * carries information to the brain regarding both sound and equilibrium. *This cross section of the cochlea shows the path the fluid vibrations will take in traveling from the upper scala vestibuli duct, through the cochlear duct and through the spiral organ of Corti. * The spiral organ of Corti contains the receptors for hearing. * Different frequencies of sound pass through the organ of Corti at different places along the cochlea which are stimulated and initiate impulses. * The impulses from the different areas of the spiral organ of Corti are interpreted by the brain as differences in pitch. * The vestibulocochlear nerve * carries information to the brain regarding both sound and equilibrium. *

103. Structure of cochlea: 2.5 turns of ducts

104. Organ of Corti

110. Inner Ear As indicated previously, * the round window * serves as the relief valve which allows the vibrations (compression waves) within the cochlea to be released into the middle ear. *As indicated previously, * the round window * serves as the relief valve which allows the vibrations (compression waves) within the cochlea to be released into the middle ear. *

112. Ear Ossicles

113. Inner Ear