Transcript Chapter 20 (Ocular Fluid).

King Saud University
College of Science
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Department of Biochemistry
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Chapter 20
Ocular Fluid
Professor A. S. Alhomida
Anatomy of the Eye
2
Anatomy of the Eye
 Cornea
•
•
Protection
Focusing
 Aqueous Humor
•
•
Shape
Nutrition
 Iris
•
•
Light control
Focusing
3
Anatomy of the Eye, Cont’d
 Lens
• Focusing
• Accommodation
 Vitreous Humor
• Shape
 Retina
• Rods: black and white, night vision
• Cones: color, day vision
• Fovea: sharpest vision (concentration of cones)
4
Anatomy of the Eye, Cont’d
 Optic Nerve
• Nerve signals to brain
• Optic Disk: blind spot
 Eye Muscles
• Eye movement
• Convergence
5
Anatomy of the Eye, Cont’d
 Sclera
• Outer walls, hard, like a light-tight box
 Pupil
• Camera aperture
 Eyelid
• Lens cover
6
Tear Production System
1. The eye's tears are composed of three layers:
•
•
•
Outermost oily layer is produced by the
meibomian glands which line the edge of the
eyelids
Watery portion of the tear film is produced by the
lacrimal gland
The mucous layer comes from microscopic goblet
cells in the conjunctiva
7
Tear Production System
2. Since the surface of the cornea is exposed
during walking hours, there is constant
evaporation of fluid on it is surface, resulting in
concentration of tear
3. Then tear becomes hyertonic (25 mosmol) that
inducing rapidly the flow of tear to be istotonic
8
Tear Production System, Cont’d
4. Diffusible nitrogous material and eletrolytes
are present in tear in concentration similar to
these of plasma
5. Function of protein is to lower the surface
tension, permit wetting of the epithelial
surfaces
6. Lysozyme is to protect the cornea from the
infection
9
Meibomian Gland
10
Lacrimal Gland
11
Conjunctiva
12
Types of Tears
1. Constant Tears
•
They formed in the accessory lacrimal glands are
continuously produced to lubricate the eye at all
times. These tears contain natural antibiotics to fight
infection
2. Reflex Tears
•
They are only produced in response to irritation, injury, or
emotion to help rinse the surface of the eye. These tears are
generated in the large lacrimal gland.
3. Between Constant and Reflex Tears
•
To a satisfactory blink reflex, helps ensure that the eyes will
be comfortable, well lubricated and well protected
13
Tear Composition
 Tear Proteins
1.
2.
3.
4.
5.
Lysozyme 300 momolar (4.6 mg/mL)
Lipocalin 74-85 mmolar (1.5 mg/mL)
Lactoferrin 24 mmolar (2 mg/mL)
Lipophilin 3 mmolar (45-100 mg/mL)
IgA (5.9 mg/mL)
14
Tear Composition, Cont’d
 Functions of Tear Proteins
•
Lysozyme
•
•
Lipocalin
•
•
Antibacterial action by cleaving cell wall
constituents
Scavenges lipids from the cornea surface, role in
tear film stability, antifungal activity by binding to
fungal siderophores, endonuclease activity
Lactoferrin
•
Antimicrobial action by competing for iron with
microbes
15
Tear Composition
16
Tear Composition, Cont’d
17
Tear Composition, Cont’d
18
Tear Composition, Cont’d
19
Aqueous Humor
1. Clear liquid lies between the cornea and the
lens
2. Produced by capillaries of ciliary bodies, exits
via Canal of Schlemm, replaced every 90 min
3. Its rate formation is 2-3 mL/min
20
Aqueous Humor, Cont’d
4. Its secretion begins with active transport of Na
into the spaces between the epithelial cells
+
5. Na pulls Cl and HCO3 along with them to
maintain the electrical neutrality
+
21
Aqueous Humor, Cont’d
6. These ions together cause osmosis of the
water from the supplying tissue into the same
epithelial intracellular spaces, and resulting
solution washes from the spaces onto the
surfaces of the ciliary processes
7. Several nutrients are transported across the
epithelial by active and passive transport
22
Aqueous Humor, Cont’d
8. Creates pressure, maintains shape, nutrients
and wastes
9. Has the benefit of being fairly homogenous
and, as a result, the optical properties are
easily measured
10. The space that it inhabits is called the
anterior chamber
23
Aqueous Humor, Cont’d
24
Eye Compartments
25
Aqueous Humor Composition
26
Aqueous Humor Composition,
Cont’d
27
Aqueous Humor Composition,
Cont’d
28
Aqueous Humor Outflow
1. Aqueous humor is produced by the ciliary body
epithelium in the posterior chamber and flows into
the anterior chamber
2. The aqueous exits the eye either through
•
3.
Conventional pathway from trabecular meshwork into
Schlemm’s canal and aqueous veins or
Unconventional pathway
•
From ciliary muscle and other downstream tissues
29
Aqueous Humor Outflow
30
Vitreous Humor, Cont’d
1. Gelatinous clear liquid lies between the lens
and the retina
2. Maintains shape of eye
3. Substances can diffuse slowly
31
Vitreous Humor, Cont’d
4. The space that it fills is called the vitreous
body or posterior segment
5. Liquefaction of vitreous humor
•
One of the most common contributing factors
for retinal detachment with ageing
32
Vitreous Humor
33
Composition of Vitreous Humor
34
Composition of Vitreous Humor,
Cont’d
35
Composition of Vitreous Humor,
Cont’d
36
Composition of Vitreous Humor,
Cont’d
37
Composition of Vitreous Humor,
Cont’d
38
Retina Structure
1. Light Sensitive Layer
•
Made of photo-receptors: rods (120 millions) and cones
(7 millions) which absorb the light
2. Plexiform Layer
•
Nerve cells that process the signals generated by rods
and cones and relay them to the optical nerve
3. Choroid
•
Carries mayor blood vessels to nourish the retina and
absorb the light so that it will not be reflected back
(dark pupil)
39
Photoreceptors
1. The transduction (conversion) of light into nerve signals that
the brain can understand takes placed in specialized cells in
the retina called photoreceptors
2. Each photoreceptor has four parts:
•
•
•
•
Outer segment
Inner segment
Cell body
Synaptic ending
40
Photoreceptors, Cont’d
3.
4.
5.
The outer segment consists of a stack of discs embedded in
the cell membrane
The photoreceptor's light-sensitive pigments are located on
these discs
It is the shape of the outer segment that distinguishes the two
main types of photoreceptors:
•
•
Rods have a long, cylindrical, outer segment with many discs
Cones have a short, tapering outer segment with relatively few discs
41
Photoreceptors, Cont’d
6.
7.
Because they have more discs, rods are over 1 000 times
more light-sensitive than cones
That is why, at night and in other low-light conditions, your
sense of vision comes from the rods alone. And conversely,
in broad daylight, your cones are more active
42
Photoreceptors, Cont’d
8.
9.
Retina has dual capabilities:
• It can work in dim light, thanks to the rods
• It can work in bright light, thanks to the cones
One of the other differences between the two types of
photoreceptors is that only the cones are sensitive to colors
43
Photoreceptors, Cont’d
44
Some of Eye Diseases
1. Dry Eye Syndrome
2. Glaucoma
3. Cataract
45
Dry Eye Syndrome
1. It is one of the most common problems treated by
eye physicians
2. It is usually caused by a problem with the quality of
the tear film that lubricates the eyes
46
Causes of Dry Eye Syndrome
1. Normal Aging Process
•
As we grow older, our bodies produce less oil – 60%
less at age 65 then at age 18. This is more
pronounced in women, who tend to have drier skin
then men
2. Contact Lens Wearers
•
Because the contacts absorb the tear film, causing
proteins to form on the surface of the lens
47
Causes of Dry Eye Syndrome
3. Certain Diseases
•
•
Thyroid conditions, and vitamin A deficiency
Diseases such as Parkinson’s and Sjogren’s
4. Other Factors
•
Such as hot, dry or windy climates, high altitudes, airconditioning, cigarette smoke and reading or working
on a computer
48
Symptoms of Dry Eye Syndrome
1.
2.
3.
4.
Itching
Burning
Irritation
Redness
49
Symptoms of Dry Eye Syndrome,
Cont’d
5. Blurred vision that improves with blinking
6. Excessive tearing
7. Increased discomfort after periods of reading,
watching TV, or working on a computer
50
Treatment of Dry Eye Syndrome
1. Eye Drops
•
Eye drops and artificial tears often offer relief for the
symptoms of Dry Eye Syndrome. The artificial lubricants
come in different thicknesses and are recommended by your
eye doctor based on the severity of symptoms and findings
2. Punctal Plugs
•
•
Through canalicular occlusion (the medical term that
describes the closure of your tear drainage ducts) there’s a
simple, non-surgical procedure to provide long-term relief of
Dry Eye Syndrome and congestion of the nose, throat and
sinus that often accompanies it
Small, non-dissolvable silicone plugs are inserted in the tear
drainage ducts
51
Treatment of Dry Eye Syndrome,
Cont’d
52
Treatment of Dry Eye Syndrome,
Cont’d
53
Glaucoma
(Sneak Thief of Sight)
1. It is a leading cause of blindness in the world,
especially for older people. But loss of sight from
glaucoma is preventable with early diagnosis and
treatment
2. It is a disease of the optic nerve that carries the
images we see to the brain
54
Glaucoma, Cont’d
3. Many people know that glaucoma has something
to do with pressure inside the eye. The higher the
pressure inside the eye, the greater the chance of
damage to the optic nerve.
4. Glaucoma can damage nerve fibers, causing
blind spots to develop
55
Glaucoma, Cont’d
5. Gradual loss of peripheral vision is the main
sign of glaucoma
6. Often people don’t notice these blind areas until
much optic nerve damage has already occurred
56
Glaucoma, Cont’d
7. If the entire nerve is destroyed, blindness results
8. Early detection and treatment by the eye doctor
are the keys to preventing optic nerve damage
and blindness from glaucoma
57
Glaucoma, Cont’d
 The optic nerve is the
nerve that takes all of the
visual information from
the retina to the brain
 It can sometimes become
swollen in diabetics
 The cause of this optic
neuropathy is unclear but
it may also be due to
insufficient blood supply
 This is an uncommon
problem in diabetics
Healthy optic nerve
58
Risk Factors for Glaucoma
1. Age
•
•
In a major study, less than 1% of people age 60 to 64 had
chronic open-angle glaucoma
Among people 10 years older, the prevalence more than
doubled to 1.3%, and among those 80 to 84, it more than
doubled again to 3%
2. Family History
•
Like so many diseases, glaucoma tends to run in
families; different genes, however, are involved in
different families
59
Risk Factors for Glaucoma, Cont’d
3. Ethnic Background
•
•
•
Chronic glaucoma is four times more common in
African-Americans than in whites
It also develops earlier: African-American risk starts to
increase after age 45, white risk at age 60
Among whites, groups at higher risk include people with
Scandinavian, Irish and Russian backgrounds
60
Risk Factors for Glaucoma, Cont’d
4. Certain Medical Disorders
•
•
•
Diabetes, extreme nearsightedness and previous eye
surgery are risk factors for chronic open-angle glaucoma
A condition that requires the use of oral or inhaled
steroids, particularly high doses for prolonged periods,
that can increase your risk as well
People who suffering from hypothyroidism, leukemia
and arthritis
61
Type of Glaucoma
1. Primary Open-angle Glaucoma
•
•
•
It affects about 4 out of 5 adult glaucoma patients
The damage to the optic nerve happens so slowly
and gradually that the affected person is usually not
aware of any loss of peripheral vision
Since there are no symptoms or pain, early
detection and treatment is the best way to prevent
loss of vision
62
Primary Open-angle Glaucoma
(A) Normal
(B) Abnormal
63
The angle between the iris and the cornea
is normal, but the drainage holes get
clogged from the inside aqueous outflow
by these pathways is diminished
Clogged Drainage holes
The Trabecular
meshwork – is the
eye’s drain
The Ciliary Body – is the eye’s
“faucet” or “tap” where fluid is
made
When this drainage of the fluid gets
blocked, excess pressure is formed
leading to Glaucoma
Normal
Drainage
Picture
64
Types of Glaucoma, Cont’d
2. Acute Closed-angle Glaucoma
•
•
•
It occurs when there is a sudden blockage of the
drainage channels in the eye
As a result, eye pressure builds up rapidly causing
blurred vision, severe pain, rainbow halos around
lights, sometimes even nausea and vomiting
It is an emergency situation, since the rapid, large
increase in intraocular pressure can cause
permanent damage to the optic nerve in only one
day
65
Acute Closed-angle Glaucoma
 Iris is abnormally
positioned so as to
block aqueous
outflow through the
anterior chamber
(iridocorneal) angle
66
The angle between iris and the cornea
narrows or closes. If fluid can’t flow
easily through the opening in the pupil,
the iris pushes forward and blocks the
drainage holes
Blocked Drainage holes
67
Glaucoma Symptoms
1. Primary Open-angle Glaucoma
•
No symptoms at first
2. Acute Closed-angle Glaucoma
•
Include severe pain, nausea, vomiting, blurred vision,
and seeing a rainbow halo around lights
68
Halo around lights
SYMPTOMS
Red eye, pain in
the eye,
Tunnel
vision
Blurred vision
Vision
loss
69
Glaucoma Treatment
1. Drug Therapy
•
•


•
•
Glaucoma medications lower intraocular pressure by
helping fluid leave the eye or by reducing the amount of
fluid produced in the eye
Prostaglandin analogs
b-lockers: Timoptic, Betoptic, Betagan, Carteolol,
Optipranolol
a-agonists
Carbonic anhydrase inhibitors
Cholinergic agents
70
71
Glaucoma Treatment, Cont’d
2. Operative Surgery
•
•
When operative surgery is needed to control
glaucoma, and creating a new drainage channel for
the aqueous fluid to leave the eye
Surgery is recommended only if the ophthalmologist
feels that it is safer to operate than to allow optic
nerve damage to continue
3. Laser Surgery
•
It creates a hole in the iris (iridotomy) to improve the
flow of aqueous fluid to the drain
72
Eye drops
Laser surgery
Pills
Eye operations
Or Combination method
73
Glaucoma Treatment, Cont’d
 Medical Treatment

Drugs increase
conventional
outflow
74
Glaucoma Treatment, Cont’d
 Medical Treatment

Drugs reduce
production of fluid in
the eye
75
Glaucoma Treatment, Cont’d
Opening Iris
 Surgical Treatment

Making a tiny
opening in the iris
with a laser allows
fluid to drain freely
Laser
76
How often should I get my eye
examined?
If you have no risk
factors for
glaucoma*
If you have risk
factor for glaucoma*
Under 45 years old:
Every 4 years
Every 2 years
45 years and older:
Every 2 years
Every year
If you are diagnosed with glaucoma, your doctor will set a treatment
cycle based upon your medical needs.
* Risk factors for glaucoma:
Family history, myopia (nearsightedness), previous eye injury, low
blood pressure, African descent, diabetes, long exposure to cortisone
77
Cataract
1. The crystalline lens of the eye focuses light rays so
that images are clear and distinct when they strike
the retina in the back of the eye
2. When the lens opacifies (gets cloudy), usually due to
aging, light rays become obstructed and vision
becomes dim and hazy
3. When this occurs, it is called a cataract
4. Heredity, disease, injury, sun exposure, and
medications can also play a role in the development
of cataracts
78
Cataract, Cont’d
 Normal lens
 Lens clouded and
discolored by cataract
79
Cataract Symptoms
1. Dimming and blurring of
vision
2. Halos around lights at night
3. Increased glare, especially at
night
80
Cataract Symptoms
4. Double vision in single eye
5. Fading or yellowing of
colors
6. Frequent changes or
cleaning of glasses
81
Types of Cataracts
1. Nuclear Cataract
•
It is most commonly seen as it forms. This cataract forms in the
nucleus, the center of the lens, and is due to natural aging
changes
2. Cortical Cataract
•
It forms in the lens cortex, gradually extends its spokes from the
outside of the lens to the center. Many diabetics develop cortical
cataracts
3. Subcapsular Cataract
•
It begins at the back of the lens. People with diabetes, high
farsightedness, retinitis pigmentosa or those taking high doses of
steroids may develop a subcapsular cataract
82
Risk Factors In Adults
1.
2.
3.
4.
5.
Exposure to sunlight (UV light)
Smoking
Diabetes
Trauma (blunt or penetrating)
Family history of cataracts
83
Risk Factors In Adults
6.
7.
8.
9.
10.
Corticosteroid therapy
Radiation exposure
Electrical injury
Myotonic dystrophy
Free radicals
•
Diet high in antioxidants, such as beta-carotene (vitamin A),
selenium and vitamins C and E, may forestall cataract
development
11. Uveitis- Ocular inflammation
84
Cataract Treatment
1.
2.
3.
Clear corneal cataract surgery
Micro incision (3 mm or <) is made into the perimeter of the
cornea on the side of the eye which is closest to the temple
Two things happen during cataract surgery
• The clouded lens is removed, and
• A clear artificial lens is implanted
85
THE END
Any questions?
86