CATARACTS: A Leading Cause of Preventable Blindness

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CATARACTS A Leading Cause of Preventable
Blindness

• Neda Karimi, M.D.
• University of Kansas Department of Ophthalmology
• August 4, 2004

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Epidemiology

• 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

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History

• 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 1700s, it was thought that
  cataract was formed by opaque material flowing,
  like a waterfall into the eye

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Lens

• 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

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Structure

• The basic lens consists of a central nucleus
  surrounded by the cortex contained within the
  lens capsule

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Optics

• 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

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Optics

• When this arrangement is disturbed in any way,
  the transparency is lost
• This results in scattering of light, blurring,
  and blocking of the image

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Structure

• 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

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Symptoms

• 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

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Hypermature Cataract

• 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

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Types of Cataract

• 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

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Nuclear Cataract

• 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

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Cortical Cataract

• 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

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Subcapsular Cataract

• 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
• This type of cataract may occur in both eyes but
  tends to be more advanced in one eye than the
  other
• Often interferes with reading vision, reduces
  your vision in bright light and causes glare or
  halos around lights at night

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Etiology

• 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

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Etiology

• 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

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Congenital Cataracts

• 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
• The eye affected by the cataract rarely achieves
  normal vision, therefore removal of the cataract
  is indicated

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Etiology of Pediatric Cataracts

• Hereditary
• Autosomal dominant form most common
• Genetic and Metabolic Diseases
• Down syndrome
• Marfans syndrome
• Myotonic Dystrophy
• Maternal Infections
• Rubella, Syphilis, Toxoplasmosis, Varicella

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• Ocular Anomalies
• Aniridia-Absence of iris at birth
• Toxic
• Corticosteroids, Radiation
• Trauma

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Risk Factors In Adults

• 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

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Risk Factors

• 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

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Clinical Findings

• The most common objective finding associated with
  cataracts is decreased visual acuity
• This is measured with an office wall chart or
  near-vision card

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Visual Acuity

• 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

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Refraction

• 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

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Slit Lamp Exam (SLE)

• 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

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Dilated Exam

• 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

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Dilated Exam

• 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

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Other Causes of painless Vision Loss

• 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

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Treatment

• 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
• 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
• 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

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Phacoemulsification

• 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

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Post-op Course

• Patients are usually examined 1 day, 1 week and
  then one month after the surgery date

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Complications of Surgery

• Vitreous Loss- 3.1
• Vitreous Hemorrhage-0.3
• Uveitis-1.8
• Increased Eye Pressure- 1.2
• Retinal Detachment- 0.7
• Endophthalmitis- 0.13

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Post Operative Period

• Contact your doctor immediately if you experience
  any of the following signs or symptoms after
  cataract surgery
• Vision loss
• Pain that persists despite the use of
  over-the-counter pain medications
• A definite increase in eye redness
• Light flashes or multiple spots (floaters) in
  front of the eye
• Nausea, vomiting or excessive coughing

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Posterior Subcapsular Opacity

• 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

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YAG Laser Capsulotomy

• A technique in which a laser beam is used to make
  a small opening in the clouded capsule to let
  light pass through

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Post YAG

• 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
• Smoking produces free radicals, increasing your
  risk of cataracts.
• Eat a balanced diet
• Include plenty of fruits and vegetables.
• Ultraviolet light protection since UV light may
  contribute to the development of cataracts
• Diabetes Control

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New Frontiers

• 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