Transcript CATARACTS - Higiene Ocupacional

CATARACTS: A Leading Cause
of Preventable Blindness
Neda Karimi, M.D.
University of Kansas Department
of Ophthalmology
August 4, 2004
Epidemiology
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Cataracts are the leading cause of
blindness in the world
More than 1.3 million cataract
procedures are performed in the U.S.
each year
Visual disability associated with
cataracts account for 8 million physician
office visits each year
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Cataract is the leading cause of
blindness in those 40 years or older in
the United States
History
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The earliest reference to cataracts can be
found in Hindu writings from the 5th century
BC
The word Cataract comes from the Greek
word meaning “Waterfall”
Until the mid 1700’s, it was thought that
cataract was formed by opaque material
flowing, like a waterfall into the eye
Lens
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The human lens is a
naturally clear
structure located
behind the iris and
supported by the
zonules
The lens is
avascular-It does
not have a vascular
supply
Structure
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The basic lens
consists of a central
nucleus surrounded
by the cortex
contained within the
lens capsule
Optics
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When light passes
through the pupil, it is
focused by the lens to
produce clear, sharp
images on the retina,
the light-sensitive
membrane on the back
of the eye that
functions like the film of
a camera
Optics
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When this
arrangement is
disturbed in any
way, the
transparency is lost
This results in
scattering of light,
blurring, and
blocking of the
image
Structure
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The lens is made mostly of water and protein
fibers
The protein fibers are arranged in a precise
manner that makes the lens clear and allows
light to pass through without interference
With aging, the composition of the lens
undergoes changes and the structure of the
protein fibers breaks down
Some of the fibers begin to clump together,
clouding areas of the lens, and leading to the
loss of transparency
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This loss of
transparency, or
opacity formation is
called Cataract
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Clouding of the lens is a normal part of aging
About half of Americans older than 65 have
some degree of clouding of the lens
According to one study, after age 75, 39% of
men, and 46% percent of women in the U.S.
have visually significant cataracts
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Cataracts produce a gradual, painless,
progressive loss of vision, and many
patients are unaware of vision problems
Generally do not cause pain, or
abnormal tearing
But as the clouding progresses, the
cataract eventually interferes with your
vision
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Commonly affect distance vision
Cause problems with glare
In the early stages, stronger lighting
and eyeglasses can help deal with the
vision problems
If impaired vision jeopardizes your
normal lifestyle, you might need
surgery
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Patients often
describe trying to
look through a
fogged-up window
Clouded vision can
make it more
difficult to drive a
car, read, or see
details
Symptoms
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Blurred vision
Increasing difficulty with vision at night
Glare, especially at night
Halos around lights
The need for brighter light for reading
Double vision in a single eye
Fading or yellowing of colors
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Due to increase of
yellow-brown
pigment in the lens,
color perception also
is affected
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These may also be symptoms of other
eye conditions, therefore it is important
to see your ophthalmologist annually, or
if there is a persistent change in vision
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Pain, redness, discharge, or irritation in
the eye are usually not signs or
symptoms of a cataract, but may be
signs and symptoms of other eye
disorders
Hypermature Cataract
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A cataract isn't
dangerous to the eye
unless the cataract
becomes completely
white, a condition
known as an overripe
(hypermature) cataract
This can cause
inflammation, eye pain
and headache
A hypermature cataract
is extremely rare and
needs removal
Types of Cataract
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The lens consists of
three layers
The outer layer is a
thin, clear membrane
It surrounds a soft,
clear material (cortex)
The hard center of the
lens is the nucleus
A cataract can form in
any part of the lens
Nuclear Cataract
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Occurs in the center of the lens
In its early stages, the patient may become
more nearsighted or even experience a
temporary improvement in reading vision
This so-called “second sight” disappears as
the lens gradually turns yellow and begins to
cloud the vision
Seeing in dim light and driving at night may
be especially troublesome
Cortical Cataract
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Begins as whitish, wedge-shaped streaks on
the outer edge of the lens cortex
As it slowly progresses, the streaks extend to
the center and interfere with light passing
through the nucleus
Both distance and near vision can be
impaired
Patients also have problems with glare and
loss of contrast
Subcapsular Cataract
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Starts as a small, opaque area just under the
capsule shell, usually at the back of the lens,
right in the path of light on its way to the
retina
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This type of cataract may occur in both eyes
but tends to be more advanced in one eye
than the other
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Often interferes with reading vision, reduces
your vision in bright light and causes glare or
halos around lights at night
Etiology
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Why age-related changes happen to the lens
is not known
One possibility is damage caused by unstable
molecules known as free radicals
Smoking and exposure to UV light are two
sources of free radicals
General wear and tear on the lens over the
years also may cause the changes in protein
fibers
Etiology
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Age-related changes in the lens are not the
only cause of cataracts
Some infants are born with cataracts or
develop them during childhood
Such cataracts may be the result of the
mother having contracted rubella during
pregnancy
Metabolic disorders
Congenital Cataracts
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Responsible for nearly 10% of all visual loss
in children worldwide
Approximately 0.03% of newborns have some
form of congenital cataract
Most are not associated with additional
developmental problems
Around one fifth of these patients have a
family history of congenital cataract but in up
to half of all cases there is no family history
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In the case of a newborn infant, a cataract
causes the immature visual system to be
deprived of the stimulation needed for normal
development
If left untreated, permanent visual loss may
occur
Unilateral cataracts are more likely to cause
visual loss because of the competition
between the two eyes
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If the cataract is small there may be only
slight blurring of vision with near normal
visual development
If the cataract is larger, or located more
posteriorly, it can effect visual development
In some cases this can lead to permanent
amblyopia (lazy eye)
Without adequate stimulation central vision
can be permanently effected
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Outcome is very much dependent on the type
of cataract
Some congenital cataracts impair visual
development only to a small degree and may
never require surgery
If the cataract is only in one eye, there is a
strong tendency for the child to prefer the
healthy eye
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The eye affected by the cataract rarely achieves
normal vision, therefore removal of the cataract is
indicated
Etiology of Pediatric Cataracts
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Hereditary
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Genetic and Metabolic Diseases
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Autosomal dominant form most common
Down syndrome
Marfan’s syndrome
Myotonic Dystrophy
Maternal Infections
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Rubella, Syphilis, Toxoplasmosis, Varicella
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Ocular Anomalies
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Toxic
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Aniridia-Absence of iris at birth
Corticosteroids, Radiation
Trauma
Risk Factors In Adults
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Exposure to sunlight (UV light)
Smoking
Diabetes
Trauma (blunt or penetrating)
Family history of cataracts
Corticosteroid therapy
Radiation exposure
Electrical injury
Myotonic dystrophy
Uveitis- Ocular inflammation
Risk Factors
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Everyone is at risk of developing
cataracts simply because age is the
single greatest risk factor
By age 65 about half of all Americans
have developed some degree of lens
clouding
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Cataracts develop sooner in diabetic
patients than in non-diabetic patients
This is caused by shifts in the glucose,
electrolyte, and water balance within
the lens
Fluctuating vision and rapid shift to
near sightedness are symptoms of
diabetes
Clinical Findings
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The most common
objective finding
associated with
cataracts is
decreased visual
acuity
This is measured
with an office wall
chart or near-vision
card
Visual Acuity
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Acuity refers to the sharpness of vision or
how clearly you see an object
In this test, your eye doctor checks to see
how well you read letters from across the
room
Eyes are tested one at a time, while the other
eye is covered.
Using the chart with progressively smaller
letters from top to bottom, to determine the
level of vision
Refraction
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This is performed by
your doctor to see if
the decrease in
vision is simply due
for need for new
glasses, or if there is
another process at
work that accounts
for the decrease in
visual acuity
Slit Lamp Exam (SLE)
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SLE allows the
ophthalmologist to see
the structures of the
eye under magnification
The microscope is called
a slit lamp because it
uses an intense slit of
light to illuminate your
cornea, iris, and lens
These structures are
viewed in small sections
to detect any small
abnormalities
Dilated Exam
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Dilating drops are
placed in the eyes to
dilate the pupils wide
and provide a better
view to the back of the
eyes
It allows the
ophthalmologist to
examine the lens for
signs of a cataract and,
if needed, determine
how dense the
clouding is
Dilated Exam
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It also allows for
examination of the
retina and the optic
nerve.
Dilating drops
usually keep your
pupils open for a
few hours before
their effect gradually
wears off
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When pupils are dilated, patients will
have difficulty focusing on close objects
With your pupils open this wide,
sunglasses are helpful on a sunny day,
and you may need a driver to drive you
home
Other Causes of painless
Vision Loss
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Cataract
Retinal detachment
Macular degeneration
Diabetes mellitus
Glaucoma
Retinal artery occlusion
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Retinal detachment is often accompanied by
floaters, flashes of light, and loss of
peripheral vision, which is often described as
a gray curtain or shade covering all or part of
the visual field
Risk factors include a history of previous
ocular trauma, nearsightedness, retinal
detachment in the fellow eye, or a family
history of retinal detachment
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Macular degeneration usually causes a
slow, progressive loss of central vision
Symptoms of acute vision loss and
distortion result from leakage from
abnormal subretinal vessels
Patients should be referred to a retina
specialist immediately
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Diabetic retinopathy may also contribute to
vision loss
Findings include dot-and-blot hemorrhages,
microaneurysms, dilated and tortuous
vessels, and neovascularization of the disk
and retina
Cataracts often obscure the fundus, making
assessment of diabetic retinopathy difficult
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Open-angle glaucoma produces slow, painless
visual field loss that usually begins
peripherally
Optic nerve damage and subsequent loss of
peripheral vision occur at normal as well as
elevated intraocular pressures
With progressive optic nerve damage and
visual field loss, central vision is the last to be
affected
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Cataracts are the most treatable cause
of decreased vision in the United States
For most patients, observation and
frequent eyeglass prescription changes
are sufficient
When activities of daily living, such as
driving, reading, working, and self-care
are affected surgery should be
discussed
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Cataract Surgery should be considered
when changes in eyeglasses no longer
help, quality of life is jeopardized, and
cataract removal is likely to have an
impact on vision
Treatment
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Make sure that eyeglasses or contact
lenses are the most accurate
prescription possible
Improve the lighting in your home with
more or brighter lamps
When outside during the day, wear
sunglasses to reduce glare
Limit night driving
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Think about how the cataract affects your
daily life
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Can you see to do your job and drive safely
Do you have problems reading or watching
television?
Is it difficult to cook, shop, climb stairs or take
medications?
How active are you? Does lack of vision affect
your level of independence?
Are you afraid you'll trip or fall or bump into
something?
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Sometimes a cataract should be
removed even if it doesn't cause major
problems with vision
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If it is preventing the treatment of another
eye problem, such as age-related macular
degeneration, diabetic retinopathy or
retinal detachment
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If you have cataracts in both eyes and
decide to have surgery, your eye doctor
typically removes the cataract in one
eye at a time
This allows time for the first eye to heal
before the second eye surgery
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Cataract surgery is the most common
operation performed on patients over 65
years of age
More than 95% of patients have improved
vision after surgery
Benefits include improvement in uncorrected
and best-corrected visual acuity, improved
binocularity, depth perception, and increased
peripheral vision to enhance patients' ability
to drive, read, work, and manage their own
medications
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Advances in surgical technique and more
sophisticated technology have helped make
surgery a safe and effective treatment for
cataracts
Prior to surgery, your eye doctor measures
the size and shape of your eye to determine
the proper lens implant power
This measurement is made with a painless
ultrasound test
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Cataract surgery is
typically an outpatient
procedure that takes
less than an hour
Most people are awake
and need only local
anesthesia
On rare occasions
some people may need
general anesthesia if
they have difficulty
laying flat or have
claustrophobia
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Two things happen
during cataract surgery
— the clouded lens is
removed, and a clear
artificial lens is
implanted
Phacoemulsification
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During
phacoemulsification,
phaco for short, the
surgeon makes a
small incision, where
the cornea meets
the conjunctiva
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The surgeon then
uses the probe,
which vibrates with
ultrasound waves, to
break up (emulsify)
the cataract and
suction out the
fragments
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Once the cataract is
removed, a clear
artificial lens is
implanted to replace the
original clouded lens
This lens implant is
made of plastic, acrylic
or silicone and becomes
a permanent part of the
eye
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Some IOLs are rigid
plastic and implanted
through an incision that
requires several stitches
(sutures) to close
However, many IOLs
are flexible, allowing a
smaller incision that
requires no stitches
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Patients usually go home the same day
Patients are seen in the office the next day,
the following week, and then again after a
month so that he or she can check the
healing progress
It's normal to feel mild discomfort for a
couple of days after surgery
You may wear an eye patch or protective
shield the day of surgery
Your doctor may prescribe medications to
prevent infection and control eye pressure
Post-op Course
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Patients are usually examined 1 day, 1
week and then one month after the
surgery date
Complications of Surgery
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Vitreous Loss- 3.1%
Vitreous Hemorrhage-0.3%
Uveitis-1.8%
Increased Eye Pressure- 1.2%
Retinal Detachment- 0.7%
Endophthalmitis- 0.13%
Post Operative Period
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Contact your doctor immediately if you
experience any of the following signs or
symptoms after cataract surgery:
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Vision loss
Pain that persists despite the use of over-thecounter pain medications
A definite increase in eye redness
Light flashes or multiple spots (floaters) in front of
the eye
Nausea, vomiting or excessive coughing
Posterior Subcapsular Opacity
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This condition occurs
when the back of the
lens capsule eventually
becomes cloudy and
blurs vision
PCO can develop
months or years after
cataract surgery
Occurs approx. 20%
percent of the time
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Treatment for PCO is simple and quick
Laser capsulotomy is a quick, painless
outpatient procedure that usually takes
less than five minutes
Capsulotomy means "cutting into the
capsule" and YAG is an abbreviation of
yttrium-aluminum-garnet, the type of
laser used for the procedure
YAG Laser Capsulotomy
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A technique in which
a laser beam is used
to make a small
opening in the
clouded capsule to
let light pass
through
Post YAG
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Afterward, patients typically stay in the
doctor's office for about an hour to make sure
the eye pressure is not elevated
In some people, particularly those who have
glaucoma or are extremely nearsighted, YAG
laser surgery can raise eye pressure
Other complications are rare but can include
swelling of the macula and a detached retina
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Most cataracts occur with age and can't
be avoided altogether
Regular eye exams remain the key to
early detection
You can take steps to help slow or
prevent the development of cataracts
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Do not smoke
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Eat a balanced diet
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Smoking produces free radicals, increasing your
risk of cataracts.
Include plenty of fruits and vegetables.
Ultraviolet light protection since UV light may
contribute to the development of cataracts
Diabetes Control
New Frontiers
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Researchers are continuing to explore
new ways to prevent and treat
cataracts, such as developing
medications that would reduce or
eliminate the need for surgery
Until then, cataract surgery is the
method to restore vision