1. EYE

2. The 6th grade science teacher, Mrs
The 6th grade science teacher, Mrs. Parks, asked her class, "Which human
body part increases to ten times its size .... when stimulated?"
No one answered until little Mary stood up, angry, and said, "You should
not be asking sixth-graders a question like that!
Mrs. Parks ignored her and asked the question again, "Which body part
increases to 10 times its size, when stimulated?"
Finally, Billy said, "The body part that increases 10 times its size .. when stimulated .. is the pupil of the eye."
Mrs. Parks said, "Very good, Billy!" Then she turned to Mary and continued,
"As for you, young lady, I have three things to say:
One, you have a dirty mind,
Two, you didn't read your homework,
Three, one day you are going to be very, very disappointed."

3. THE EYE
Structures Surrounding the Eye
The eye is in the orbit of the skull for protection.
Within the orbit are 6 extrinsic eye muscles, which move the eye.
There are 4 cranial nerves: Optic (II), Occulomotor (III), Trochlear (IV), and Abducens (VI).
Eyelids are PALPEBRA, and eyelashes are CILIA.
Fun fact: there is a new medicine to make you grow longer eyelashes!
People of Asian descent have an EPICANTHIC FOLD in the upper eyelid; no functional difference.
Around the eyeball are glands.

4. Surface Anatomy of Eye

5. Extrinsic Eye Muscles
Figure 16.6a, b

6. FUN FACTS Do eyelashes grow back?
Eyelashes take about four to eight weeks to grow back.
What purpose do eyebrows serve?
To keep the sweat and rain out of our eyes. The arch shape of the eyebrow diverts rain or sweat down our cheeks, keeping our eyes dry. Eyebrows also help us to communicate. Sometimes a raised eyebrow is more effective than words.
The Mona Lisa has no eyebrows. In the Renaissance era, it was fashion to shave them off !

7. Eyelashes

8. GLANDS OF THE EYE
1. LACRIMAL GLANDS are the largest set. They are on the superior lateral eyelid and they produce tears, which drain into the nasal cavity via the LACRIMAL DUCT.
The function is to moisten and lubricate the eye surface, and it has enzymes to kill bacteria (which thrive in warm, moist conditions).

9. Figure 16.5b

10. GLANDS OF THE EYE
2. LACRIMAL CARUNCLE (“little meat”) is the spot on the medial corner of the eye. It makes an oily secretion like a sebaceous gland.
The function is to lubricate the eye a little bit for the eyelids. When the secretion dries, it is called “sand” in the eyes.

11. GLANDS OF THE EYE
3. TARSAL GLANDS are sebaceous glands on the inside of the eyelid, and produce sebum, which is an oil to lubricate the eyeball.
Therefore, the oil component found in tears is produced by the tarsal glands.
The tarsal glands and the lacrimal caruncle make a waterproof surface so the eye won’t dry out.
When tarsal glands are clogged = CHALAZION

12. Chalazion

13. GLANDS OF THE EYE 4. CILLIARY SEBACEOUS GLANDS go to only the cilia.
When clogged = STY.

14. Dry Eye Syndrome
Sty

15. FUN FACTS An ostrich's eye is bigger than it s brain!
Is the human eye fully grown at birth?
A typical newborn's eye is around 18 millimeters in diameter. A fully grown adult's eye measures millimeters. A fully developed eyeball is about two-thirds the size of a ping-pong ball.
This means a human eye grows only about 28% over the course of its life. Fish supposedly have the ability to increase their eye size "steadily over the course of their entire lives," a talent lost on us.

17. NOTE
When you are referring to a structure that has a cavity (stomach, esophagus, uterus, eye, etc), the layer that touches the lumen is considered the superficial layer, even though from the outside of the body it would be considered deeper.
Therefore, the choroid layer is deep to the retina.

18. Ora serrata
Rods and cones

19. The Eyeball
1. CONJUNCTIVA is like a Saran Wrap covering around the eye and under the eyelids. It’s made of stratified columnar epithelium (the first time in the body we’ve seen this tissue).
It also has lots of goblet cells to secrete moisture for those areas.
Deep to the epithelium is loose connective tissue with lots of small blood vessels, which are not seen unless the conjunctiva becomes inflamed:
Blood-shot eyes: just from being tired
PINK EYE (layman’s term), known as CONJUNCTIVITIS (from bacteria, very contagious).

20. The Eyeball 2. FIBROUS TUNIC is the next layer, and has 2 parts:
A. SCLERA is the white of the eye, made of dense irregular connective tissue. It is continuous with the dura mater of the brain. The eye is part of the brain. The sclera protects the eye.
B. CORNEA is clear, and avascular (no blood supply) except around the periphery. Therefore, there is no tissue rejection when it is transplanted into another person; there is also no need to find a donor match. It has lots of pain receptors, so a scratched cornea is very painful. Its function is to be the main focuser of light for the eye. If damaged, need a corneal transplant.

21. Scleritis

22. Conjunctivitis

23. The Eyeball
3. VASCULAR TUNIC is deep to the fibrous tunic. It has several structures.
A. CHOROID has lots of blood vessels and pigment. The function of the pigment is to absorb excess light so it does not reflect off other cells and cause too many action potentials. The blood vessels provide blood supply to the other layers.
B. CILIARY MUSCLES surround the lens.
C. SUSPENSORY LIGAMENTS (also known as the zonule) hold the lens in place.
D. LENS functions to continue to focus the light after it passes through the cornea. It changes shape to allow you to distinguish close from far. The lens changes shape by the ciliary muscles pulling on the suspensory ligaments.

24. The Vascular Tunic
PLAY
Vascular Tunic (Uvea)
Figure 16.8

25. Rods and cones

26. Figure 16.7a

27. Figure 16.9a

28. Ciliary Muscles
When you are looking far away, the ciliary muscles are relaxed, the lens is stretched into a wide circle, and the suspensory ligaments are tight.
When you look up close, the ciliary muscle contracts and gets smaller, to the ligaments relax. Constantly looking close puts strain on the ciliary muscles = EYE STRAIN.

29. Pupils
Fun Fact: -When you are looking at someone you love, your pupils dilate, and they do the same when you are looking at someone you hate.

30. PROBLEMS WITH THE LENS
With age, the lens loses flexibility, and is less likely to round up.
It stays in the position for seeing far, so there is trouble focusing on things that are near = PRESBYOPIA (“old eyes”).
Occurs around age
It is far-sitedness because the LENS cannot accommodate.

31. PROBLEMS WITH THE LENS
Clouding of the lens leads to a clinical condition known as CATARACTS.
Treatment is to remove the lens and replace it with a plastic one (which is not flexible either).
If the lens yellows, you can’t see the color blue. After surgery, can see blue again.

32. Cataract

33. Cataract Surgery VIDEO
Cataract Vision
Cataract Surgery VIDEO

34. IRIS (the colored part of the eye)
The function is to constrict or dilate the pupil (opening) to allow light in.
Therefore, it regulates the amount of light passing to the visual receptors of the eye.
If there is a lot of pigment, eye is brown; a medium amount = green, small amount = blue, no pigment = pink (albino).

43. Iris
Doctors are now using laser to remove the melanin from the iris to change a person’s brown eyes to green or blue!

44. FUN FACTS Why are all babies born with blue eyes?
Melanin is a brownish pigment that adds color to your hair, eyes, and skin. At the time babies are born, melanin hasn't yet been "deposited" in the eyes' iris. Hence, they appear blue.
After about six months, eyes change color depending on the amount of melanin. If you have a lot of it, your eyes will turn brown or black. If you have little, they'll stay blue. And if you have no melanin, your eyes may appear pink. Interestingly, as the site notes, human beings aren't the only creatures with freaky color-morphing eyeballs. Kittens experience the same phenomenon.
How can someone have two different colored eyes?
Eye color is a polygenic trait. Many babies are born with blue eyes.

45. RETINA The retina is on top of the choroid layer.
The retina is made up of PHOTORECEPTORS, which are sensors for light.

46. Rods and cones

47. Figure 16.7a

48. Fovea centralis
Optic Nerve

49. Rods and Cones Two types of photoreceptors: Rods and Cones.
1. CONES (red, green, and blue) they have less light sensitivity (poor at night) but see colors well. There is a region on the retina that has the highest concentration of cones; it is called the FOVEA CENTRALIS. The fovea centralis is the very center point of a small circular region called the MACULA. When you want details, focus the light on the macula, because there are a lot of cones there. The other layers contain a mixture of both.

50. Figure 16.7a

51. Test for Colorblindness

53. Rods and Cones
2. RODS have more light sensitivity (can see well at night) but does not see colors well.
Above the photoreceptors are layers of neurons that send their axons out to form the optic nerve.

54. Fovea centralis
Optic Nerve

55. Retina
Figure 16.10a

56. Photoreceptors
Figure 16.11

57. Blind Spot at the Optic Nerve
The region where the optic nerve leaves and blood vessels come into the eye has no photoreceptors = BLIND SPOT.
Hold your hands out at 45° and that’s the location of the blind spot.
You can still see your hands because the other eye sees it. Close your right eye and look for your right hand and you’ll find the blind spot.

58. Figure 16.7a

59. Find your blind spot! Stare at the center of X and move head closer until one red spot disappears

60. Blind Spot
The light takes a path through the cornea and lens to the blood vessels that are entering the eye, so this is the only place in the body where you can see blood vessels directly.
The doctor can diagnose hypertension and diabetes by looking in the eye.
On a clear, bright day, look at the blue sky and you can see the shadow of your own blood vessels on the photoreceptors as criss-cross lines in field of vision. The little moving dots are your blood cells.

61. Normal Retina

62. The visual information travels from the retina deep into the brain through the optic chiasma (not visible with an opthalmascope).
From here, it goes into the occipital lobe of the brain, where it is processed.

63. Cranial Nerves II, III, IV, VI

64. OPTHALMASCOPE
An opthalmascope is the instrument used to look inside the eye.
The doctor can see the optic disc, fovea centralis, macula, the lens, retina, and blood vessels.

66. PROBLEMS WITH VISION
FLOATERS are when a capillary breaks and/or some cells break off and get stuck in the jelly-like fluid in the posterior cavity of the eye.
Floaters don’t actually move, the eye just tries to track them.

67. Floaters

68. Floaters
Floaters can best be seen when the person looks at a clear blue sky or white wall.

69. RETINAL DETACHMENT The retina separates from the underlying choroid.
Retinal detachment can be caused from a blow to the eye, or may occur spontaneously. Usually caused by an injury like a blow to the eye with a baseball, punch, or airbag to the eye.
It may not cause blindness immediately. Although the detached portion contains capillaries, it is separated from the main blood supply, so if it is not lasered back into place within two hours, permanent blindness can result.
Cells in the retina die from lack of oxygen. Manifests as a shimmering light. This is considered a medical emergency and needs immediate treatment. Those who are most vulnerable to spontaneous detachment are those who are nearsighted.

70. HYPEROPIA (far-sighted) eyes are too short MYOPIA (nearsighted) eyes are too long

71. The Eye as an Optical Device
Figure 16.14a–c

72. Hyperopia and Myopia
Normal eyes are perfect spheres. When the eyeball is not a perfect sphere, the lens has to accommodate as much as possible, and corrective glasses are usually needed.
Myopic eyes are elongated. Even badly nearsighted eyes are only 1mm from normal. Treatments are glasses or Lasix, which is laser surgery on cornea, when it’s shaved so it focuses light farther back to reach the retina.

73. Lasik Surgery: VIDEO

74. Hyperopia and Presbyopia
Hyperopia and presbyopia have some features in common (they are both far-sighted), but the key difference between these two conditions is that in hyperopia the lens can accommodate, but in presbyopia it cannot.

77. ASTIGMATISM
ASTIGMATISM is when the cornea has an irregular shape. Part of the field of view is out of focus.
The eyeball changes shape until age 24.

78. Astigmatism Test

79. Astigmatism Vision

80. MACULAR DEGENERATION
The size of the macula is the size of the printed letter “O” in 14 pt font. When the macula degenerates, you lose a lot of sight. This is the most common cause of blindness in the US.
It’s due to bleeding in the eye, causing scar tissue. The retina does not get enough oxygen, and the cells die. Macular degeneration allows vision in the periphery, but they can’t read or drive.

81. Macular Degeneration

82. Macular Degeneration What it is like to go blind Surgery VIDEO
Surgery VIDEO

83. Macular Degeneration
Unusual condition causes woman to hallucinate scary faces. Charles Bonnet syndrome
Charles Bonnet syndrome (CBS) is a condition that causes patients with visual loss to have complex visual hallucinations.

84. DIABETIC RETINOPATHY
This is when the high sugar levels destroy the photoreceptors in the retina.
The blood vessels also swell and rupture and the clots block vision.
Some of this damage can be repaired by using a laser to evaporate the blood clots, but any damage to the photoreceptors is permanent. It can lead to blindness.

85. Diabetic Retinopathy

86. Diabetic Retinopathy

87. Diabetic Retinopathy vision

89. INTERNAL STRUCTURES OF THE EYE
There are two cavities
Anterior Cavity
Posterior Cavity

90. Anterior Cavity
1. ANTERIOR CAVITY is anterior to the lens, and is filled with AQUEOUS HUMOR, similar to plasma, supplies nutrients to the cornea and lens.

91. Figure 16.7a

92. GLAUCOMA
GLAUCOMA is increased pressure within the anterior chamber of the eye. It leads to blindness.
This form of blindness is more common in third-world countries because we have tests to detect it and treat it.
The test measures how much pressure there is here by seeing how easily the cornea is deformed, either with air or direct pressure. How many of you have had this test?

93. Glaucoma

94. Glaucoma Test
Darker areas are fields of blindness

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96. 2. POSTERIOR CAVITY is filled with VITREOUS HUMOR, which is jelly-like, and helps give shape to the eyeball. It leaks out from a cut, you’ll go blind because the body can’t replace it.
The four main things that cause blindness are macular degeneration, cataracts, glaucoma, and diabetic retinopathy.
ARTIFICIAL EYES VIDEO

97. AMBLYOPIA
AMBLYOPIA = Lazy Eye. In a child, one eye will track and focus, the other won’t.
If untreated in children, eventual blindness in weak eye because the brain will shut down in the occipital lobe.
Treatment is to patch the good eye to force the bad eye to make the connections, or a surgery to weaken the muscle to make the strong side just as weak.

98. Ptosis
Ptosis (Greek "fall") is a drooping of the upper or lower eyelid.
The drooping may be worse after being awake longer, when the individual's muscles are tired.

99. Ptyerigium
Pterygium (Surfer's Eye) is a benign growth of the conjunctiva. A pterygium commonly grows from the nasal side of the sclera.
It is thought to be caused by ultraviolet-light exposure (sunlight), low humidity, and dust.

100. Cancer of the Eye: Choroidal Melanoma

101. Live worm in the eye

102. NOTE
If a child is blind until age 4-5, and then you restore the sight, he will still be blind because the brain doesn’t form properly.
Kids can have astigmatism or weak eye muscles, one eye stops seeing (or sees double), or congenital cataracts.
The thalamus in the brain will shut off all the signals from the bad eye.

103. NOTE
To protect your eyesight throughout your life, use the rule:
Every 20 minutes look up for 20 seconds at something 20 feet away.
The rest of this lecture is not on the exam!

104. The red lines are straight!

105. Look at the dot and move your head forward and back

106. Look at the dot and move your head forward and back

107. Stare at the + for 30 seconds and the pink dots will disappear!

108.
The photo is in black and white.
Stare at the dot in the center until the timer counts down to zero.
The photo will now appear to be in color!
It's black and white but the orange saturated the color receptors other then blue so you see blue in the sky etc...
If your color receptors are being saturated by one color and there is another complementary color present it will stand out more.

109. FUN FACTS ABOUT VISION Why do you cry when you cut onions?
It releases an enzyme that reacts with the amino acids in the onion that create an acid that diffuses into the air and irritates your eyes. Scientists have tried to make a non-crying onion, but it turns out that enzyme is needed for the onion flavor. You can heat the onion before chopping or chop under running water. Use canola oil on your knife before you cut the onion and you won’t cry. Or order take-out.
Do cucumbers relieve puffy eyes?
No, they are just cool and filled with water, so the cooling effect reduces the swelling.

110. FUN FACTS ABOUT VISION Can carrots help improve your vision?
This myth dates back to WWII when the British Royal Air Force was attempting to hide the fact that they developed a new radar system to shoot down German bombers. They bragged that the great accuracy of thie British fighter pilots at night was a result of them being fed an enormous amount of carrots. It is true that carrots contain beta carotene which converts to vitamin A which is needed to prevent night blindness, but we only need a small amount, and having more than that will not improve vision. In fact, too many carrots can cause your skin to turn orange.

112. FUN FACTS ABOUT VISION
Can you lose a contact lens in the back of your head?
No; the underside of the eyelid is connected to the sclera (white part of the eye).
Why do you get bags under your eyes when you are tired?
The skin under the eyes is the thinnest in the body, and it allows the dark, venous blood to show through. Dark rings tend to be genetic and get worse as you age. Good rest and nutrition minimizes the rings.

113. FUN FACTS ABOUT VISION Should you put a steak on a black eye?
It doesn’t do any more good than an ice pack
Does hysterical blindness really exist?
Yes. There is a device that can check for someone faking blindness; they put a black and white spinning pinwheel in front of the eyes, and if you can see, your eyes will automatically move a little back and forth.

114. FUN FACTS ABOUT VISION
Why do you see stars when you are hit in the head?
It happens to Wile E. Coyote every time he gets hit on the head with an anvil by the Road Runner. Yes, it can happen, and it indicates there is a concussion. The visual area of the brain has hit against the inside of the skull.
Will staring at an eclipse make you go blind?
The intense light burns some of the cells in the retina, but it doesn’t cause complete blindness.

115. FUN FACTS ABOUT VISION
Why is it impossible to sneeze with your eyes open?
Sneeze impulse affects a variety of body parts, including the abdomen, chest, neck, and face. During a sneeze, the impulses that travels through your face causes your eyelids to blink. This response is entirely automatic. There's nothing you can do about it. Sneezing puts a lot of pressure on your head and respiratory system, so blinking is probably a protective mechanism.
The point is that all of these responses (the abdominal contraction, the sharp burst of air out of your lungs, the general lunging movement) are intertwined.

116. FUN FACTS ABOUT VISION
Can a person who is blind from birth "see images" in their dreams?
People who are visually impaired from birth appear to lack visual imagery in their dreams but have a “very high percentage of gustatory, olfactory, and tactual sensory references," something very unusual for sighted dreamers to experience.

117. What kind of nightmares do blind people have?
I was strapped to a chair in a damp room. I couldn't make sense of the room I was in, the echo's were too confusing and ever-changing. Then I hear footsteps, followed by the laughter of a young child. Suddenly someone charges in and kicks one of the legs from under my chair. It quickly vanishes. Then the laughter again, this time I can hear its from a young girl. Its a mocking laugh. Again someone charges in and kicks another leg from under the chair. I start to wobble. I feel water at my feet. It's rising. Another leg from under the chair and more laughter. I don't know where the person is, but I know it's there, looking at me, pointing at me. Finally the last leg is kicked from under the chair and I fall down on the concrete floor. The water is at my mouth and freezing cold, I can't move my body. Just as I am about to drown, I wake up.

118. FUN FACT OR FICTION? Extensive computer usage can cause dry eyes.
Fact. Extensive computer use can lead to dry eyes. A person experiencing minor amount of dryness will feel much worse after prolonged computer use. Studies have shown that computer users tend to stare at the screen without blinking for a long time, which may cause dry eyes. Dry eyes are one of the factors leading to Computer Vision Syndrome. Thus frequent blinking is essential to lubricate the eyes and prevent them from drying.

119. FUN FACT OR FICTION?
Sitting close to a television set, movie or computer screen can harm your eyes.
Fallacy. Our eyes are not harmed by viewing these at a short distance. There is, however, a greater likelihood of experiencing eye fatigue or a headache.

120. FUN FACT OR FICTION? Reading in dim light is harmful to your eyes.
Fallacy. For centuries, all night time reading and sewing was done by candlelight or with gas or kerosene lamps. Reading in dim light does not damage the eyes. However, good lighting does make reading easier and prevents eye fatigue, especially for people who wear bifocals.

121. Computers and eyestrain
Computers can put stress on the eyes causing headaches, blurred vision and eye fatigue. The following steps can be taken to reduce eyestrain:
Computer screen is at least 18 to 26 inches away from your eyes.
Arrange the monitor so that the top line of on-screen text is at eye level. Placing a monitor too high exposes more of the eye, causing it to dry out.
Arrange lighting to minimize glare and reflections.
Keep the computer screen clean and dust-free to minimize glare.
Take frequent vision breaks to stretch your body and rest your eyes.
Remember to blink often to keep your eyes moist.
Place reference material alongside and as close to the computer screen as possible to avoid frequent head and eye movements and focusing changes.

122. Television and your eyes
Never watch TV in a completely darkened room. The best lightning conditions consist of a back light and dim general light in the room.
Place the set to avoid glare and reflections from lamps, windows and other bright sources.
View from a distance at least five times the width of the television screen.
Have the set at approximately eye level.
Wear lenses prescribed for vision correction.
Avoid staring at the screen. Briefly look away from the picture, around the room.

123. Avoid eye strain while reading
Keep the reading material at the best distance: place knuckles under your chin and book under the elbow. Try to avoid reading while lying on your back, stomach, or side. Make sure that there is good light on close work tasks and good room light as well. A light positioned behind and over one's shoulder works well for reading. Also, looking up from time to time from your reading can help keep your eyes relaxed.