Cataract Surgery
What is a cataract?
Imagine
that the eye is like a camera (A). Into it there are two lenses (1) to
focus the outside images over a sensible film (2) which will form the
photographic image (Figure 1). In the human eye these lenses are, first, the
CORNEA (1), which is the most powerful external lens in the eye. Once you get
in the eye, you find the second lens also known as CRYSTALLINE (3), which is
located behind the diaphragm formed by the IRIS (2). For approximately 50
years during a human’s lifetime, the CRYSTALLINE’s mission is to help in
distinguishing the different distances between objects, which one is further
away and which one is closer to you.
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A
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B
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Figure 1: Comparison between the elements which form a camera (a) and the human
eye(B)
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It is, indeed, the loss of transparency of this last lens which is known by the term
CATARACTS.
Before continuing, it is precise to clarify some errors or mistaken ideas about the Cataracts. A Cataract
IS NOT:
- A membrane that covers the eye.
- A result of using too much the eyes.
- A cancer.
- A contagious disease that can be transmitted from a person to another one or from an eye to the
other.
- They never cause irreversible blindness by themselves.
What causes the cataracts?The
main cause of the aparition of cataracts has to do with the natural ageing of
the eye. Nevertheless, there are some factors which can precipitate or induce
cataract formation
- Inheritance: There
is an existant genetical or family predisposition in the appearance of
cataracts
- Eye injuries, such as serious traumatisms or
infections.
- General diseases, such as Diabetes.
Along
the normal evolution of the crystalline, it can become hard and lose
transparency, causing SENILE CATARACTS. They are the most
frequent form of cataracts and are usually formed in people aged 40.
Traumatisms
caused on eyes can lead to cataract formation. Their aparition does not depend
on age and its development is fast. These would be known as TRAUMATIC
CATARACTS.
Some
infections, medications, or diseases, such as Diabetes, can cause SECONDARY
CATARACTS formation.
Cataracts
can develop in children as well and have a very fast development. They can be
caused by a infection or inflamation during pregnancy. This type of cataracts
are called CONGENITAL CATARACTS.
What symptoms have?Although
the symptoms of catarcacts can vary from one patient to another, especially due
to their location or their quick formation, some frequent symptoms are:
- Vision
becomes blurred, as a light fog or like watching trought a breaded glass, in
any case without pain.
- Dazzle or increase of light sensivity.
- Frequent
need of change in eyeglass graduation, that generally causes an eye to become
myopic, and at the same time improves nearby vision.
- Need of
an intense light to be able to read.
- Worse
vision at night.
- Possibility
of seeing two images with one eye.
- Most
colors slowly disappear and have a tendency to become yellowish.
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A
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B
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Figure 3. Simulation of the
cataract effects on the vision. We can see how the image turns cloudy
and a reduction of contrast and luminosity. The image acquire yellow
colors.
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Diagnosis and detection
Cataracts
cannot usually be detected only observing an eye without the help of medical
instruments. If any of this symptoms is detected, you must go to the
ophtalmologist to examine your eyes.
The ophtalmologist examines the eyes with a series of instruments to
determine the size, location and evolution of cataracts, and also looks for any
other alteration which can cause similar symptoms.
TREATEMENT:
Surgery
is the only way to eliminate the cataracts. At the moment, there are no
medicines, nutritional supplements, exercices, or optical instruments to cure or
delay cataract evolution.The
right moment to begin the treatement varies depending on the symptoms caused by
cataracts and their hardness degree.
It is not true that the cataracts
have to be "mature" before it can be operated, nor
that a person has to wait to barely see before deciding to be submitted to
surgery. Thanks
to present-day techniques, with a very low surgical risk and the developement in
the implantation of "Artificial Crystalliness", the right
moment to extract the cataracts is when the patient feels a slightly worse
visual sharpness that doesn’t allow him to carry on with his life in a normal
way.
Another
factor that determines if cataracts have to be extracted is their way of
developement, and if your ophtalmologist thinks that these could increase
surgical risks or injure your eyes (a madurity excess, an ocular Hypertension
caused by disease in the crystalline, etc)..
PREOPERATING PREPARATIVES
Before surgery, it is necessary to make a series of tests to prepare the
pacient’s eye or general body to avoid possible unexpected situations that can
later cause complications during surgery or in the surgical results
It is
necesary that your Family Doctor makes a general check to analize your heart and
your lungs before surgical intervention. A blood analysis has to be made too to
complete the study of your general body health. (These tests will be asked for)
A few
days before surgery, and in this ophtalmological center, an ecography of your
eye will be taken to determine, by Ultrasounds, the power and characteristics of
the Artificial Crystalline which must be implanted during the surgery.
The day
before surgery, a few farm eyedrops have to be smoothly dropped on the eye which
will eventually be operated, to reduce the inflammatory reaccions caused after
surgery, and an antibiotic farm eyedrop.
The day
of the surgical interaction, once the patient in the clinic room, the
nurses will, when ordered, have to expand the pupil with a few farm eyedorops.
Simultaneously, the antibiotic and anti-infalammatory treatment started the day
before will be repeated.
Local anesthesia in
the surgery
Cataract surgery is carry out with TOPICAL ANESTHESIA
and a light SEDATION. This means that only the eye that will be
operated will be sedated with a contact farm eyedrop, and to
get rid of the anxiety caused in the patient due to the operation.PRE-ANESTHESIC
GENERAL RULES:
- The
patient must not have any drink or food orally before surgery
during at least 8 hours. It is
usually recomended not to have any food after the previous night’s supper
- The use
make-up and fingernail coloration will be avoided because they could hide
external signs of pallor, cyanosi (blueish face due to lack of oxygen), etc.
- The
patient must leave their prosthesis (fake teeth, etc.), and personal
belongings such as rings, bracelets, and necklaces in the clinic room, for
these objects could produce injuries during his sleep state.
Anesthetic technique
Once
the patient is in the operating room, the doctor in charge of anesthesia, after
having verified the general explorations and confirmed possible alergies, will
proceed to canalize a vein, if possible located on the back of the hand to
administrate:
- ANTIBIOTIC
MEDICATION: which will be administered to prevent possible infections on the
zone to be operated.
- SEDATIVE
MEDICATION: will allow a high comfortability in the patient during the surgery,
as well as avoiding a possible pain when injecting the local anethesia in the
eye.
- ANTI-INFLAMMATORY:
in any operated zone, smaller or greater inflammatory proceses are produced
and are necesary to try to be reduced.
- SERUM-THERAPY:
during surgery, serum will be administrated (containing electrolytes and
glucose) to counteract the hours passed without nutrition as well as to keep
the circulatory system intact. Serum-therapy is usually taken away after
surgery, unless other conditioning factors advise its continuation.
The anesthesia of the eye is administered by farm
eyedrops to "anesthetize" it. The eye will not feel any pain at all.
Nevertheless, the eye’s mobility is not eliminated, so it can move
freely.
For this reason it is important to try to collaborate with the surgeon
and try to fix your glance and follow his directions to make the actions during
the surgery easier.
The patient will reamain
with a light grade of sedation during the surgery. At the same time his vital
constants will be controlledPOSTOPERATIVE:
The cataract surgery usually is made in ambulatory
regime. The patient is registered, normally, after he has reinitiated the
feeding by oral way (3 hours after the anesthesia). In some cases it is possible
to advance the exit of the patient and to allow that he begins the feeding in
his home.
The patient will be
informed of the medication he can take (mainly analgesics) and the postoperative
personal rules he will have to follow. A recently operated patient must not
drive any kind of vehicle.
LITTLE FREQUENT COMPLICATIONS:
- Allergic
reactions that
can possibly happen because of medicine.
- Respiratory
depression
consecutive to the sedative administration.
Surgical technique
Basically, cataract surgery consists on eliminating the
altered material of the crystalline, and to replace it with a synthetic material
which carries out the same functions as a natural crystalline.
Nowadays, to achieve this, a surgical technique knowed as "FACOEMULSIFICATION"
of the crystalline with implantation of intraocular lenses is followed.
Once in the surgical room,
with the topic anesthesia already administered, and always under the anesthesic
doctor’s supervision, the zone around the eye to be operated is proceeded to
be “painted" with an antiseptic solution. The patient is covered with
sterile sheets (Statures) to minimize the risk of infections, and under
microscopic control, the surgery begins.
(A)
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Figure 4: (A): General image of a typical Operating room of ophtalmology where it is possible to
appreciate the Operating room table (1), the Microscope (2), the equipment of Resuscitation (3) and the equipment of Ophtalmology surgery (4).
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The first step is to make a small “valvulated” incision of
2.5mm of amplitude approximately in the edge of the cornea (Figure 6A). Trough
it we can acces the cataract.
Next, a portion of the external capsule that surrounds
the crystalline is retired.
By means of a special "Probe" that contains an ultrasound
emisor, an aspiration system and a liquid irrigation one, we begin with the
fracture and aspiration of the altered crystalline (Cataract "Emulsification")
(Figure 6B) respecting the capsule which held the crystalline.
In this capsule is where
the new ARTIFICIAL CRYSTALLINE , or INTRAOCULAR LENS will be
located. It is made of flexible material, such as silicone and acrylics, and is
introduced through the small incision previously made.
After
checking if the "Intraocular lens" is positioned correctly, and if
the it works as a watertight valve, an Anti-infalmatory and Antibiotic
ophtalmoligical farm eyedrop is administered and the eye will remain open
without protection.
POSTOPERATIVE CARES:
Thanks
to the present "aspiration" technic of the cataract, the implantation
of a Intraocular Lens and mainly because of the minimal incisions made, no
stitches are needed to closed the scar. The operated eye is ready to support any
activity once the patient leaves the operating room. However, it is advised that
during the first 24 hours physical efforts and abrupt movements of the head
should be avoided. YES YOU CAN:
- Read.
- Watch T.V.
- Travel in any type of transport (car, metro, bus, etc.)
- Walk (Not run)
- Duck (without raising weigths)
- Sleep sideways (it would be better not to sleep on the
side of the operated eye the first night)
The
same or the next day after surgery, once you are in the doctor's office, the
operated eye will be examined and the ambulatory treatment will start(in your
house) with Antibiotics and Anti-inflamatory farm eyedrops with the prescribed
dose..
WAY OF ADMINISTERING THE FARM
EYEDROPS:
For a rigth farm eyedrop administration, the eyelid
must be depressed smoothly while the patient looks upwards and a drop will be
deposited i the "bottom of the sack" of the conjunctive (Figure 7).
The farm eyedrops can be
administrated one after the other without having to wait any time between them
or any order.
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(Figure7).Way
of administrating farm eyedrops: gently presion the lower eyelid and let a
drop fall in the “bottom sack” of the conjunctive.
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Complications:
Thanks
to new advances of the technique used, cataract surgery has experimented a
considerable reduction in some serious complications that took place before,
such as retinal injuries, Detatchements of Retina, Glaucome, Corneal Injuries,
deformations in the form and position of the pupil, and especially the
dependancy on corrector crystalls of high graduation (over 12 Dioptres for
distant vision). Nevertheless, and in spite of all the precautions that can be
taken, the possibility that a new complication appears still exists. . PREVIOUS
COMPLICATION TO THE SURGERY:
- Mistakes
in the Ultrasound measurement
Due to
the different hardnesses between one cataract and the other, if an eye is
extreamly large (myopic) or short (hipermyopic), or in some cases due to the
difficulty of the patient to watch the fixation light of the Ultrasound Machine,
some computational mistakes are made. A mistake would cause a calculation
failure on the power of the Intraocular Lens, and therefore, a graduation
deffect would appear after surgery. If the graduation deffect is not hight, the
solution would be to wear eyeglasses, or if desired, it can be solved with the
Laser Excimer (LASIK). If it were to be very high, the lens must be extracted
and replaced.
COMPLICATIONS DURING THE SURGERY:
The
complications during surgery are usually related to the maturity degree and
evolution of the cataracts, so the more "mature" they are, the higher
the risk presented. They do not represent any clinical problem for the patient,
although surgery would last longer and the postoperative time of recovery would
be extended.
- Capsular
Breakage of the Crystalline: Generally takes place when trying to suction a
very advanced cataract, becoming the most frequently "Per-surgery"
complication. This breakage consists on the rip of the capsule where the
crystalline is located. Depending on the extension of the breakage, it could
provide difficulties when positioning the Artificial Crystalline in the Sack
and having to change the location of this Crystalline.
- Luxation
of the "Crystallinean masses": As a result of a Capsular breakage,
the content of this sack (the cataracts), can fall into a place called
“Vitreous Cavity” in the eye, and it would be necessary to recuperate them.
- Luxation
of the Artificial Crystalline: Caused by the same complications as the
previous section. The Intraocular Lens must be replaced in it usual position
to get a more stable location.
- Technical
transformation: This can happen in such excessively advanced and hardened
cataracts, that the Endo-Ocular fracture system cannot break down the
cataracts. In this case, the incision must be extended and the crystallinean
masses taken out. This technique demands the use of sutures to close the
"injury" and consequently extend the process of visual recovery.
COMPLICATIONS AFTER THE SURGERY:
- Corneal
Edema (inflamation): Causes visual cloudiness. This is normal during the first
24-48 hours, nevertheless this inflamation can be rated from intense to very
intense because of the following -reasons
- Complications
during surgery.
- Bad
state of the cornea before surgery (corneal decompensation)
- Ocular
Hypertension as a more extended reaction.
- Endoftalmitis:
This is the most serious and severe complication that can happen after a
surgical intervention. It consists on a serious infection in the eye. Thanks
to a great knowledge of the contamination mechanisms and especially the strict
asepsis control (desinfection) and atibiotic pre-medication the
percentage of aparition of this complication has been reduced to really low
numbers. The succes of its recuperation is based on the quick and
energetic elimination of the ocular infection.
- Itch,
sensation of strange eye-shape, sporadic pricks, etc: As a consequence of the
healing processes of the small injury that has been made.
Contrary
to the thought of many patients, the "Rejection of the Intraocular
Lens", is a practically nonexistent complication. The materials used in it
manufacture, the treatment that maded over this materials to make them
biologically stable, and the anatomic seat in the eye, make it practically
imposible for a rejection rection along the patient’s life to happen. It is
for that reason that the Intraocular lenses can be implanted safely even in
children with Congenital Cataracts during the first months of their life.
