Cataracts

Cataracts

Definition
The lens of the eye is normally transparent. A
cataract is a condition in which the lens of the eye
becomes cloudy or opaque. This cloudiness can impair
vision and may lead to eventual blindness.

Description
The human eye has several parts. The outer layer of
the eyeball consists of a transparent dome-shaped cornea
and an opaque, white sclera. The cornea and sclera help
protect the eye. The next layer includes the iris, pupil,
and ciliary body. The iris is the colored part of the eye
and the pupil is the small, dark, round hole in the center
of the iris. The pupil is primarily responsible for allowing
light into the eye. The ciliary body contains muscles
that help the eye focus. The lens, which lies behind the
pupil and iris, is covered by a cellophane-like capsule. It
is normally transparent, elliptical in shape, and somewhat
elastic. Due to this elasticity, the lens can focus on
both near and far objects. The lens is attached to the ciliary
body by fibers (zonules of Zinn). Muscles in the ciliary
body act on the zonules, which then change the
shape of the lens. This process is called accommodation—
the lens focuses images to help make vision clear.
As people age, the lens hardens and changes shape less
easily. As a result, accommodation becomes more difficult,
making it harder to see things up close. This normal
aging condition, called presbyopia, generally occurs
around age 40 and continues until about age 65.
Individuals with this condition generally need reading
glasses.
The lens is made up of approximately 35% protein
and 65% water. As people age, degenerative changes in
the lens’s proteins occur. Changes in the proteins, water
content, enzymes, and other chemicals are some of the
reasons for the formation of a cataract.
The major areas of the lens are the nucleus, the cortex,
and the capsule. The nucleus is in the center of the
lens, the cortex surrounds the nucleus, and the capsule is
the outer layer. Opacities can occur in any area of the
lens, and cataracts can be classified according to their
location (nuclear, cortical, or posterior subcapular
cataracts). The density and location of the cataract determines
the amount of vision affected. If the cataract forms
in the area of the lens directly behind the pupil, vision
may be significantly impaired. A cataract that occurs on
the outer edges or side of the lens causes less visual
impairment.
Cataracts in the elderly are so common that they are
thought to be a normal part of aging. Cataracts affect
about 50% of individuals between the ages of 52-64,
while at least 70% of those 70 and older are affected.
Cataracts associated with aging (senile or age-related
cataracts) are usually bilateral (occur in both eyes) with
asymmetric progression (different rates of progression).
Initially, cataracts may not affect vision. If the cataract
remains small or at the periphery of the lens, the visual
changes may be minor.
Cataracts are much less common in younger people.
Congenital cataracts are rare in newborns. When they do
occur, they may be due to genetic defects or an infection
or disease in the mother during pregnancy. Traumatic
cataracts may develop after a foreign body or trauma
injures the lens or the eye. Systemic illnesses, such as
diabetes, also may result in cataracts. Cataracts can occur
secondary to other eye diseases—for example, uveitis or
glaucoma. Such cataracts are called complicated
cataracts. Toxic cataracts result from chemical toxicity,
such as steroid use. Cataracts also can result from exposure
to the sun’s ultraviolet (UV) rays.

Causes and symptoms
Recent studies have investigated the effect of nutrition
on cataract formation. The results have been mixed,
with some studies finding that there is a connection
between nutrition and cataract formation and other studies
finding none. Much interest has been focused on the use of
antioxidant supplements as a protection against cataracts.
Antioxidants, such as vitamins A, C, E, and beta-carotene,
help the body neutralize oxygen-free radicals.
Smoking and alcohol intake, however, have been
implicated in cataract formation, as have the use of oral
corticosteriods and antihypertensive agents. Some studies
have determined that a diet high in fat increases the
likelihood of cataract formation, while an increase in
foods rich in antioxidants reduces the incidence. More
research is needed to determine the precise role played by
diet, smoking, alcohol consumption, and antioxidants in
the formation of cataracts.
Some unrelated physical conditions, such as diabetes
mellitus, also may contribute to cataracts. Eye
injuries and sun exposure also are causative factors.
There are several common symptoms of cataracts:
• gradual, painless onset of blurry, filmy, or fuzzy vision
• poor central vision
• frequent changes in eyeglass prescriptions
• changes in color vision
Cataracts
• increased glare from lights, especially oncoming headlights
when driving at night
• “second sight” improvement in near vision (no longer
needing reading glasses)
• poor vision in sunlight
• presence of a milky whiteness in the pupil as the
cataract progresses

Diagnosis
Ophthalmologists and optometrists detect and monitor
cataract growth and prescribe prescription lenses
for visual deficits. Ophthalmologist perform cataract
extraction.
Cataract diagnosis begins with a complete eye exam.
The ophthalmic assistant, technician, or nurse gathers
information to determine the progression of the vision
loss. It is unusual for cataracts to cause rapid vision loss,
but sometimes patients believe the vision problem is
acute because vision in the better eye has only recently
been compromised. Patient history includes a review of
refractive history, previous ocular disease, ambylopia,
eye surgery, and trauma. Ophthalmic personnel also
question patients about difficulties driving, reading, and
performing daily activities, and record any medication
the patient currently uses.
The ocular exam determines the severity of the
cataract and assesses other factors that might contribute
to the potential for good vision after surgery. The exam
includes measurement of visual acuity under both low
and high illumination, biomicroscopy with pupillary
dilation, stereoscopic fundus examination with pupillary
dilation, assessment of ocular motility and binocularity,
visual fields, evaluation of pupillary responses, refraction,
and measurement of intraocular pressure (IOP).

Treatment
No treatment may be necessary for cataracts that
cause no symptoms or that cause only minor visual
changes. It is important for an ophthalmologist or
optometrist to continue to monitor and assess the cataract
during regular office visits. Increased strength in prescription
eyeglasses or contact lenses may be diagnostic
and beneficial.
Cataract surgery—the only option for patients
whose cataracts interfere with vision to the extent that
their daily activities are affected—is the most frequently
performed surgery in the United States. It generally
improves vision in more than 90% of patients. Most
cataracts are removed before the lens is completely
opaque or mature. This is done to minimize the impact of
the cataract on the patient’s daily life and also to decrease
the risk of other eye complications. Sometimes cataracts
need to be removed so the surgeon can examine the back
of the eye more carefully. This is important in patients
with diseases that may affect the eye. If cataracts are
present in both eyes, surgery is performed on one eye at
a time. The first eye heals before the second cataract is
removed, sometimes as soon as the following week. A
final eyeglass prescription is usually given about four to
six weeks after surgery. Patients will still need reading
glasses. The overall health of the patient must be considered
in making the decision to have undergo cataract surgery.
However, age alone need not preclude effective surgical
treatment of cataracts, and people in their 90s can
have successful return of vision after cataract surgery.
Surgery to remove cataracts is generally an outpatient
procedure. A local anesthetic is used, and some
newer techniques take only minutes to complete.
Removal of the cloudy lens can be accomplished with
one of the three types of cataract surgery available:
• Extracapsular cataract extraction. In this type of
cataract extraction, the lens and the front portion of the
capsule are removed. The back part of the capsule
remains in place.
• Extracapsular cataract extraction by phacoemulsification.
This type of extracapsular extraction requires only
a very small incision, resulting in faster healing.
Ultrasonic vibration is applied to the lens to break it up
into very small pieces, and the ophthalmologist then
aspirates the pieces out of the eye with suction. As of
2001, this is the most commonly performed type of
cataract surgery.
• Intracapsular cataract extraction. The lens and the
entire capsule are removed. This method carries an
increased risk for detachment of the retina and swelling
after surgery, and, as a result, it is rarely used.
442 GALE ENCYCLOPEDIA OF NURSING AND ALLIED HEALTH
A replacement lens is inserted at the time of the surgery.
A plastic artificial lens called an intraocular lens
(IOL) is placed in the remaining posterior lens capsule of
the eye. When the intracapsular extraction method is
used, an IOL may be clipped onto the iris. Contact lenses
and cataract glasses (aphakic lenses) are prescribed if
an IOL cannot be inserted due to complications. A folding
IOL is used with the phacoemulsification procedure
to allow it to pass through the small incision.
Antibiotic drops to prevent infection and steroids to
reduce inflammation are prescribed after surgery. An eye
shield or glasses protect the eye from injury while it
heals. During the night, an eye shield is worn. The patient
returns to the doctor the day after surgery for assessment,
with several follow-up visits over the next two months to
monitor the healing process. Return visits at three and six
months are optional.

Prognosis
The cataract extraction success rate is very high with
a good prognosis. A visual acuity of 20/40 or better is
expected as a result of cataract extraction. If an extracapsular
cataract extraction was performed, a secondary
cataract may develop in the remaining back portion of the
capsule. This can occur one to two years after surgery.
YAG capsulotomy is most often used for this type of
cataract. YAG stands for yttrium aluminum garnet, the
name of the laser used for this procedure. This is a painless
outpatient procedure and requires no incision. The
laser beam makes a small opening in the remaining back
part of the capsule, allowing light through.
Complications occur in a very small percentage (3-
5%) of surgical cataract extractions. Possible complications
include infections, corneal edema (swelling),
diplopia, bleeding, retinal detachment, iris prolapse or
vitreous in the wound, intraocular lens dislocation, and
Cataracts

KEY TERMS
Glaucoma—Disease of the eye characterized by
increased pressure of the fluid inside the eye.
Untreated, glaucoma can lead to blindness.
Ultraviolet radiation (UV)—Invisible light rays
that may be responsible for sunburns, skin cancers,
and cataract formation.
Uveitis—Inflammation of the uvea. The uvea is a
continuous layer of tissue which consists of the
iris, the ciliary body, and the choroid. The uvea
lies between the retina and sclera.
the onset of glaucoma. Some problems may occur one to
two days, or even several weeks, after surgery. Follow-up
examinations should check the patient for haziness or
redness in the eye, decrease in vision, nausea, and pain.

Health care team roles
Skilled ophthalmic technicians and assistants record
the patient history and perform many of the preliminary
tests. Depending on skill level, these ophthalmic assistants
may perform measurement of visual acuity under
both low and high illumination, biomicroscopy with
pupillary dilation, assessment of ocular motility and
binocularity, visual fields, evaluation of pupillary
responses to rule out afferent pupillary defects, refraction,
and measurement of intraocular pressure (IOP).
Before the surgery, nurses and assistants also prepare
the operating room (OR). Many ophthalmologists now
have their own ambulatory surgery centers (ASCs) where
skilled technicians and ophthalmic nurses play a critical
role in preparing the OR and patients for the surgery.
Ophthalmic nurses also assist the ophthalmologist during
surgery and discuss outcomes with patients postoperatively.

Patient education
When a cataract is found, the patient should be
informed, even if surgery is not immediately indicated.
The optometrist or ophthalmologist should discuss the
different treatment options, as well as the risks and benefits
of surgery with the patient.

Prevention
The eyes should be protected from UV radiation by
wearing glasses with a special coating. Dark lenses alone
are not sufficient, but the lenses must be coated to filter
out UV light (specifically, UV-A and UV-B). Antioxidants
also may help prevent cataracts by reducing free radicals
that can damage lens proteins. A healthy diet rich in
sources of antioxidants, including citrus fruits, sweet
potatoes, carrots, green leafy vegetables, and/or vitamin
supplements, may be beneficial. When taking certain
medications, such as steroids, more frequent eye exams
may be necessary. Patients should also be told not to
smoke.