What is a cataract? A cataract is an opacity or
cloudiness in the natural lens of the eye. It is
still the leading cause of blindness worldwide and
represents an important cause of visual impairment
in the United States. The development of cataracts
in the adult is related to aging, sunlight exposure,
smoking, poor nutrition, eye trauma, systemic
diseases, and certain medications such as steroids.
A single study has suggested that use of oral
vitamin C may help delay the progression of
cataracts. Just as a smudged or dirty camera lens
may spoil a photograph, opacity in the natural lens
of the eye can result in a blurred image. Patients
with cataracts usually complain of blurred vision
either at distance, near, or both. This may
interfere with tasks such as driving or reading.
Other common complaints include glare, halos, and
dimness of color vision.
Diagnosis
A diagnosis of cataract can only be
made by a thorough eye examination including slit
lamp (microscopic) evaluation. Other devices are
sometimes used to determine if glare interferes with
vision. If cataract surgery is being considered, an
ophthalmologist will also examine the posterior
aspect of the eye, which will include evaluation of
the retina and optic nerve.
The progression of
cataracts is highly variable, however, they will
invariably worsen in severity. Changing glasses may
sometimes be useful in improving vision as the
cataract progresses, since cataracts may induce
relative nearsightedness. This is the answer as to
why some patients with hyperopia (farsightedness)
will actually have better vision without glasses in
the early stages of cataract development. For most
patients, however, changing glasses has minimal
impact on overall visual quality. Besides changing
glasses, the only other option for treatment of
cataracts is cataract surgery.
Decision for Cataract Surgery
The decision for cataract surgery is reached only between the EyeMD
and the patient. In general, this decision is based
on the degree to which the patient’s vision is
impaired, and the impact that impairment has on his
or her quality of life. When a patient is
significantly bothered by symptoms of cataract,
cataract surgery is usually offered. Many patients
will ask if a cataract must be “ripe” before
surgery. The answer with today’s technology is “no.”
Before the development of small incision cataract
surgery and intraocular lens implants, outcomes with
cataract surgery were far inferior to outcomes
today. Therefore, ophthalmologists would typically
wait until a cataract was very advanced before
offering surgery. Today, with advanced surgical
techniques and equipment, cataract surgery can be
offered at a much earlier stage. In fact, most
ophthalmologists will agree that it is safer to
proceed with cataract surgery at an earlier stage of
development rather than waiting until the cataract
is advanced and very dense.
Selecting the right intraocular lens
When a cataract is removed, it is
replaced with an artificial intraocular lens (IOL).
There are a variety of IOLs that can be used in
cataract surgery, and they each have their own set
of advantages and disadvantages. No single IOL works
best for everyone, and only your ophthalmologist can
determine the most appropriate IOL for your needs.
The FDA approval process for IOLs is among the most
rigorous in the world. You can rest assured than any
IOLs used in the U.S. have undergone very extensive
testing for safety and efficacy. These same IOLs are
also used for a refractive surgery procedure known
as refractive lens exchange. In refractive lens
exchange, the IOL is used solely in an attempt to
reduce or eliminate the need for glasses or contact
lenses. This article outlines some of the choices of
IOLs that are available for use in cataract surgery
and refractive lens exchange.
Fixed Focus Monofocal
IOLs are used in the majority of cataract procedures.
These lenses have the advantage of excellent quality
distance vision under a variety of lighting
conditions. Since these lenses have a fixed focal
point which is generally set for distance vision,
reading glasses are typically required for good near
vision(1). For patients willing to use reading
glasses for near tasks, these IOLs are an excellent
choice. Several million lenses of this variety have
been used for decades with an excellent safety
record. Recent refinements in the optical quality of
these lenses have allowed an even higher quality of
vision than previously achievable.
 |
|
The ReStore Lens
made by Alcon, a second generation
multi-focal implant. |
Multifocal IOLs use a different strategy to
achieve good distance and near vision without
glasses. These lenses have highly specialized
optical properties that can divide light to bring it
into focus at more than one point at the same time.
This allows the eye to see both near and far,
usually without glasses. Excellent results for
distance and near vision have been achieved by both
of the FDA approved lenses of this type. The ReZoom™
multifocal IOL has several zones of optical power
that are designed to provide good vision at varying
distances, under varying lighting conditions. In a
clinical study, 92 percent of ReZoom™ IOL patients
reported never or only occasionally having to wear
glasses. Another multifocal IOL is the ReSTOR™. This
IOL uses a patented diffractive optical design to
divide light into two focal zones so that near and
distance objects can both be seen without glasses.
An impressive 80% of patients from the ReSTOR FDA
trial reported that they never wore glasses after
the procedure(3). Multifocal IOLs have a slightly
greater tendency to cause night vision complaints
than other IOLs, so those who drive a great deal at
night may wish to consider a different IOL. The vast
majority of patients with these IOLs are not
bothered by night vision complaints, however.
The Procedure
Cataract surgery today is typically performed using a
microincisional procedure. To the patient, this
means minimal discomfort during or after surgery, a
more speedy recovery of vision, and reduced risk of
induced astigmatism. This means less dependence on
glasses afterwards.
Below, we’ve detailed the major steps of cataract
surgery using a microincision procedure,
phacoemulsification (ultrasonic cataract removal),
and a foldable lens implant. This type of procedure
is considered state-of-the-art for cataract surgery
today. The procedure demonstrates basic principles
only, however, and eye surgeons use many variations
of the general theme, even from one case to another,
depending on the type of cataract being removed.
The most commonly used cataract incision is about 3
millimeters in size – just about one-eighth of an
inch! Because of the careful construction of this
incision, and its small size, the incision is
generally self-sealing. This translates to a
“no-stitch” type operation.
The surgeon then creates an opening in the capsule,
which is a micro-thin membrane surrounding the
cataract. This procedure, called capsulorhexus,
requires extraordinary precision since the capsule
is only about four-thousandths of a millimeter
thick! This membrane is actually thinner than a red
blood cell and the surgeon must delicately remove
the capsule while manipulating instruments within
the anterior chamber – a space only 3 millimeters deep!
Phacoemulsification is the aspect of the procedure
in which ultrasonic vibrations are used to break the
cataract into smaller fragments. These fragments are
then aspirated from the eye using the same
instrumentation.
The surgeon may elect to create grooves in the
cataract, and subsequently break the cataract into
smaller pieces using the phacoemulsification tip and
a second instrument passed through a smaller
“side-port” incision.
The lateral view of the procedure shows the
phacoemulsification tip being placed into the
substance of the cataract by the eye surgeon.
The “phaco” aspect of the procedure is used to
remove the denser central nucleus of the
cataract.
Once the denser central nucleus of the cataract has
been removed, the softer peripheral cortex of the
cataract is removed using an irrigation/aspiration
handpiece. The The posterior, or back side, of the
lens capsule is left intact to help support the
intraocular lens (IOL) implant.
The intraocular lens is often folded and passed
through the tiny incision where it is opened
(implanted) inside the “capsular bag”. In this
illustration, the lens is being inserted via an
“injector”. This is an instrument designed to help
keep the incision size small while allowing
implantation of a 6 millimeter lens through a 3
millimeter (or even smaller) incision!
The IOL is shown here implanted within the “capsular
bag” where it is neatly centered. The springy “arms”
of the IOL, known as haptics, hold the lens implant
within the capsular bag. The IOL does not generally
require sutures to remain in good position.
This lateral view of the IOL implant shows the lens
within the “capsular bag,” which is the desired
location. This position is the same as that of the
natural lens (cataract) of the eye and, therefore,
is generally tolerated best and provides the most
optimal visual results. At this stage, the cataract
operation with IOL implantation is complete.
What to Expect During Surgery
Modern cataract surgery is performed almost
exclusively on an outpatient basis. Most patients
will be asked to arrive at the surgery center about
an hour prior to surgery. Prior to surgery, a number
of eye drop medications will be applied to the eye
to prevent pain, to reduce inflammation and the risk
of infection, and to fully dilate the pupil. The
surgery is typically performed under local or
topical anesthesia. With local anesthesia, the
entire eye and eye muscles are numbed to prevent
discomfort. With topical anesthesia, just the front
of the eye is numbed. Either type of anesthesia
allows the procedure to be performed painlessly. The
type of anesthesia chosen depends on surgeon
preference and many patient variables.
During surgery, most patients remain fully awake,
however, mild sedation may be used depending on
physician and patient wishes. The patient is asked
to lie still during surgery and, if the procedure is
performed with topical anesthesia, the patient will
usually be asked to look toward the light of the
operating microscope. Surgery is usually completed
in just 20 to 30 minutes. Patients are asked to
remain still during the procedure and to inform the
surgeon if needing to cough or otherwise move for
any reason. Once the surgery is complete, the
patient will be briefly monitored, post-op
instructions given, and in most cases, the patient
may be discharged to home within an hour.
What to Expect After Surgery
After discharge from the surgery center, patients
will usually be asked to return for a follow-up
visit later that day or the next day, however, this
will be based on individual circumstances. Also
depending on the type of incision and surgeon
preference, some patients will be asked to wear a
shield over the eye, particularly while sleeping.
The eye should not be rubbed, or pressure placed
directly on the eye through the eyelid, during the
first few weeks following surgery. Eye drop
medications will be required, usually consisting of
antibiotic and anti-inflammatory medicines. These
will often be tapered off during the first month
after surgery.
The best vision may not be obtained until several
weeks following surgery, but individual results vary
considerably, depending on many variables. The great
majority of patients may resume normal activities on
the day of or day after surgery. Activities such as
reading, watching television, and light work will
not hurt the operated eye. Most surgeons arbitrarily
recommend waiting 4 to 6 weeks before new glasses
are obtained. This allows the eye to achieve
considerable stability from a refractive standpoint
and, therefore, the glasses prescription should be
accurate and relatively stable.
Many patients are surprised at how clear their
vision is after cataract surgery. Some patients may
have better vision than they ever did before
cataract surgery. Furthermore, depending on the
degree of refractive error (need for glasses) prior
to surgery, many patients will be much less
dependent on glasses for far vision than they were
before surgery. Patients will often notice that
colors are brighter and more brilliant. The results
are often dramatic
Potential Complications with Cataract surgery
Though cataract surgery is one of the most successful
procedures in all of medicine, complications may
still occur. Potential complications range from
devastating visual loss to minor inflammation in the
eye following surgery. In general, the risk of
severe visual loss is very rare, but may occur as a
result of infection or bleeding inside the eye, or
even retinal detachment, which may occur months or
years after a perfectly successful cataract
procedure. Most complications are minor, such as
swelling of the cornea or retina, increased pressure
in the eye, and droopy eyelid. These complications
usually resolve with medications and continued
healing time.
Over 98% of cataract surgeries are successfully
completed without surgical complications, and more
than 95% of patients have improved vision. Those
patients whose vision fails to improve often have
underlying ocular disorders, such as age related
macular degeneration (ARMD), diabetic retinopathy,
and other conditions. In some cases, these patients
may benefit from other procedures or from low vision
aids.
Envision Your Future
Cataract surgery today is truly a miracle of modern medicine. With
the collaborative efforts of physicists,
bioengineers, and EyeMDs, modern cataract surgery
has reached a new pinnacle of success. If your
vision has faded as a result of cataracts, your
likelihood of recovering more youthful vision with
cataract surgery is exceedingly high. If you choose
to have cataract surgery, you will likely enjoy a
rapid recovery of enhanced vision with little
disruption to your lifestyle.
|
