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Cataract surgery is the removal of the natural lens of the
eye (also called "crystalline lens") that has developed an
opacification, which is referred to as a cataract. Metabolic changes of the
crystalline lens fibers over time lead to the development of the cataract and
loss of transparency, causing impairment or loss of vision. Many patients'
first symptoms are strong glare from lights and small light sources at night,
along with reduced acuity at low light levels. During cataract surgery, a
patient's cloudy natural lens is removed and replaced with a synthetic lens to
restore the lens's transparency.
surgical removal of the natural lens, an artificial intraocular lens implant is
inserted (eye surgeons say that the lens is "implanted"). Cataract
surgery is generally performed by an ophthalmologist (eye surgeon) in an
ambulatory (rather than inpatient) setting, in a surgical center or hospital,
using local anesthesia (either topical, peribulbar, or retrobulbar), usually
causing little or no discomfort to the patient. Well over 90% of operations are
successful in restoring useful vision, with a low complication rate. Day care,
high volume, minimally invasive, small incision phacoemulsification with quick
post-op recovery has become the standard of care in cataract surgery all over
Types of surgery
There are three
main types of cataract surgery:
Phacoemulsification (Phaco) is the preferred method in most cases. It involves
the use of a machine with an ultrasonic handpiece equipped with a titanium or
steel tip. The tip vibrates at ultrasonic frequency (40,000 Hz) and the
lens material is emulsified. A second fine instrument (sometimes called a
"cracker" or "chopper") may be used from a side port to
facilitate cracking or chopping of the nucleus into smaller pieces.
Fragmentation into smaller pieces makes emulsification easier, as well as the
aspiration of cortical material (soft part of the lens around the nucleus).
After phacoemulsification of the lens nucleus and cortical material is completed,
a dual irrigation-aspiration (I-A) probe or a bimanual I-A system is used to
aspirate out the remaining peripheral cortical material.
extracapsular cataract extraction (ECCE): Extracapsular cataract extraction
involves the removal of almost the entire natural lens while the elastic lens
capsule (posterior capsule) is left intact to allow implantation of an
intraocular lens. It involves manual expression of the lens through a large
(usually 10–12 mm) incision made in the cornea or sclera. Although it
requires a larger incision and the use of stitches, the conventional method may
be indicated for patients with very hard cataracts or other situations in which
phacoemulsification is problematic.
cataract extraction (ICCE) involves the removal of the lens and the surrounding
lens capsule in one piece. The procedure has a relatively high rate of
complications due to the large incision required and pressure placed on the
vitreous body. It has therefore been largely superseded and is rarely performed
in countries where operating microscopes and high-technology equipment are
readily available. After lens removal, an artificial plastic lens (an
intraocular lens implant) can be placed in either the anterior chamber or sutured
into the sulcus.
a form of ICCE that freezes the lens with a cryogenic substance such as liquid
nitrogen. In this technique, the cataract is extracted through use of a
cryoextractor — a cryoprobe whose refrigerated tip adheres to and freezes
tissue of the lens, permitting its removal. Although it is now used primarily
for the removal of subluxated lenses, it was the favoured form of cataract
extraction from the late 1960s to the early 1980s.
The surgical procedure
in phacoemulsification for removal of cataract involves a number of steps. Each
step must be carefully and skillfully performed in order to achieve the desired
result. The steps may be described as follows:
2. Exposure of
the eyeball using a lid speculum,
3. Entry into the
eye through a minimal incision (corneal or scleral)
injection to stabilize the anterior chamber and to help maintain the eye
destruction or emulsification of the cataract after nuclear cracking or
chopping (if needed), cortical aspiration of the remanescent lens, capsular
polishing (if needed)
of the, usually foldable, intra-ocular lens (IOL)
11. Wound sealing
/ hydration (if needed)
The pupil is
dilated using drops (if the IOL is to be placed behind the iris) to help better
visualise the cataract. Pupil-constricting drops are reserved for secondary
implantation of the IOL in front of the iris (if the cataract has already been
removed without primary IOL implantation). Anesthesia may be placed topically
(eyedrops) or via injection next to (peribulbar) or behind (retrobulbar) the
eye. Oral or intravenous sedation may also be used to reduce anxiety. General
anesthesia is rarely necessary, but may be employed for children and adults
with particular medical or psychiatric issues. The operation may occur on a
stretcher or a reclining examination chair. The eyelids and surrounding skin
will be swabbed with disinfectant. The face is covered with a cloth or sheet,
with an opening for the operative eye. The eyelid is held open with a speculum
to minimize blinking during surgery. Pain is usually minimal in properly anesthetised
eyes, though a pressure sensation and discomfort from the bright operating
microscope light is common. The ocular surface is kept moist using sterile
saline eyedrops or methylcellulose viscoelastic. The discission into the lens
of the eye is performed at or near where the cornea and sclera meet (limbus =
corneoscleral junction). Advantages of the smaller incision include use of few
or no stitches and shortened recovery time.
(rarely known as cystotomy) is a procedure to open a portion of the lens
capsule, using an instrument called a cystotome. An anterior capsulotomy refers
to the opening of the front portion of the lens capsule, whereas a posterior
capsulotomy refers to the opening of the back portion of the lens capsule. In
phacoemulsification, the surgeon performs an anterior continuous curvilinear
capsulorhexis, to create a round and smooth opening through which the lens
nucleus can be emulsified and the intraocular lens implant inserted.
cataract removal (via ECCE or phacoemulsification, as described above), an
intraocular lens is usually inserted. After the IOL is inserted, the surgeon
checks that the incision does not leak fluid. This is a very important step,
since wound leakage increases the risk of unwanted microrganisms to gain access
into the eye and predispose to endophathalmitis. An antibiotic/steroid
combination eye drop is put and an eye shield may be applied on the operated
eye, sometimes supplemented with an eye patch.
be administered pre-operatively, intra-operatively, and/or post-operatively.
Frequently a topical corticosteroid is used in combination with topical
operations are performed under a local anaesthetic, allowing the patient to go
home the same day. The use of an eye patch may be indicated, usually for about
some hours, after which the patient is instructed to start using the eyedrops
to control the inflammation and the antibiotics that prevent infection.
peripheral iridectomy may be performed to minimize the risk of pupillary block
glaucoma. An opening through the iris can be fashioned manually (surgical
iridectomy) or with a laser (called Nd-YAG_laser iridotomy). The laser
peripheral iridotomy may be performed either prior to or following cataract
hole is larger when done manually than when performed with a laser. When the
manual surgical procedure is performed, some negative side effects may occur,
such as that the opening of the iris can be seen by others (aesthetics), and
the light can fall into the eye through the new hole, creating some visual
disturbances. In the case of visual disturbances, the eye and brain often learn
to compensate and ignore the disturbances over a couple of months. Sometimes
the peripheral iris opening can heal, which means that the hole ceases to
exist. This is the reason why the surgeon sometimes makes two holes, so that at
least one hole is kept open.
surgery, the patient is instructed to use anti-inflammatory and antibiotic eye
drops for up to two weeks (depending on the inflammation status of the eye and
some other variables). The eye surgeon will judge, based on each patient's
idiosyncrasies, the time length to use the eye drops. The eye will be mostly
recovered within a week, and complete recovery should be expected in about a
month. The patient should not participate in contact/extreme sports until
cleared to do so by the eye surgeon.
after cataract surgery are relatively uncommon.
* PVD — Posterior
vitreous detachment does not directly threaten vision. Even so, it is of
increasing interest because the interaction between the vitreous body and the
retina might play a decisive role in the development of major pathologic
vitreoretinal conditions. PVD may be more problematic with younger patients,
since many patients older than 60 have already gone through PVD. PVD may be
accompanied by peripheral light flashes and increasing numbers of floaters.
* Some people can
develop a posterior capsular opacification (also called an after-cataract). As
a physiological change expected after cataract surgery, the posterior capsular
cells undergo hyperplasia and cellular migration, showing up as a thickening,
opacification and clouding of the posterior lens capsule (which is left behind
when the cataract was removed, for placement of the IOL). This may compromise
visual acuity and the ophthalmologist can use a device to correct this
situation. It can be safely and painlessly corrected using a laser device to
make small holes in the posterior lens capsule of the crystalline. It usually
is a quick outpatient procedure that uses a Nd-YAG laser
(neodymium-yttrium-aluminum-garnet) to disrupt and clear the central portion of
the opacified posterior lens capsule (posterior capsulotomy). This creates a
clear central visual axis for improving visual acuity. In very thick opacified
posterior capsules, a surgical (manual) capsulectomy is the surgical procedure
performed. A YAG capsulotomy is, however, a factor which must be taken in
consideration in the event of IOL replacement as vitreous can migrate toward
the anterior chamber through the opening hitherto occluded by the IOL.
capsular tear may be a complication during cataract surgery. The rate of
posterior capsular tear among skilled surgeons is around 2% to 5%. It refers to
a rupture of the posterior capsule of the natural lens. Surgical management may
involve anterior vitrectomy and, occasionally, alternative planning for implanting
the intraocular lens, either in the ciliary sulcus, in the anterior chamber (in
front of the iris), or, less commonly, sutured to the sclera.
detachment is an uncommon complication of cataract surgery, which may occur
weeks, months, or even years later.
* Toxic Anterior
Segment Syndrome or TASS is a non-infectious inflammatory condition that may
occur following cataract surgery. It is usually treated with topical
corticosteroids in high dosage and frequency.
is a serious infection of the intraocular tissues, usually following
intraocular surgery, or penetrating trauma. There is some concern that the
clear cornea incision might predispose to the increase of endophalmitis but is
no conclusive study to corroborate this suspicion.
* Glaucoma may
occur and it may be very difficult to control. It is usually associated with
inflammation, specially when little fragments or chunks of the nucleus get
access to the vitreous cavity. Some experts recommend early intervention when
this condition happens (posterior pars plana vitrectomy). Neovascular glaucoma
may occur, specially in diabetic patients. In some patients, the intraocular
pressure may remain so high that blindness may ensue.
* Swelling or
edema of the central part of the retina, called macula, resulting in macular
edema, can occur a few days or weeks after surgery. Most such cases can be
* Other possible
complications include: Swelling or edema of the cornea, sometimes associated
with cloudy vision, which may be transient or permanent (pseudophakic bullous
keratopathy). Displacement or dislocation of the intraocular lens implant may
rarely occur. Unplanned high refractive error (either myopic or hypermetropic)
may occur due to error in the ultrasonic ecobiometry (measure of the length and
the required intra-ocular lens power). Cyanopsia, in which the patient sees
everything tinted with blue, often occurs for a few days, weeks or months after
removal of a cataract. Floaters commonly appear after surgery.