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WHAT ARE THE
IN REFRACTIVE SURGERY?
It is my hope to inform you concerning the side
effects, limitations and complications of laser refractive surgery. It is a
struggle to balance the benefits of laser surgery with the known and the unknown
risks. Please understand this important message:
It is impossible to perform any form of surgery without
risks. All patients need to be willing to accept a certain degree of
responsibility for these risks.
My intention is not to frighten or dissuade someone
from pursuing laser surgery, as most of my patients will never encounter any
serious complications, and the vast majority are pleased with the improvement
they achieve. It is my intention, however, to accurately outline the associated
risks to all candidates so that they may either elect not to accept the risks
associated or be better prepared to deal with any unexpected complication or
side effects. The only way in which a patient can avoid all surgical risks is by
not proceeding with surgery.
There is a risk of
with all laser refractive surgery. The risk of serious infection is far
less in LASIK than in PRK. The risk is reduced five fold from approximately 1/100 with PRK to 1/5000 with LASIK.
Refractive problems that
may be encountered include too much correction, too little correction, a
prescription imbalance between eyes, aggravation of muscle imbalance problems or
a loss of effect from regression. LASIK and PRK may result in over
corrections and under corrections due to the variability in patient healing
patterns and other surgical variables, leaving patients nearsighted, farsighted,
or with astigmatism. This may or may not require patients to wear
spectacles, contact lenses or undergo further surgery.
Incidence of significant over correction: 1 in 100
Incidence of significant under correction: varies with
There is a risk of PAIN
with all laser refractive surgery, the risk of pain is far less in LASIK than in
PRK. This risk of pain is reduced fivefold from approximately 1/10 with PRK to 1/50 with LASIK. It is
common to feel a mild foreign body sensation similar to an eyelash sensation.
It is common for patients to have some;
light sensitivity, tearing, mild redness and swelling following the surgery.
The risk of
(see photo) from
LASIK is less than 0.5%, this is 1/5 to 1/10 the rate as compared to PRK. The
risk of scar tissue formation with PRK ranges from 1-5%, increasing in incidence
with the degree of attempted correction, Scar tissue is composed of collagen
proteins which develop on the surface of the eye with PRK and beneath the
corneal flap with LASIK. It presents usually as a dirty windshield type of
appearance to your vision.
Night Glare is common in
nearsighted individuals even before any refractive procedure is performed but
increases almost immediately in the healing process and is more common when only
one eye has been treated. Typically, 6 months after both eyes have been treated,
only 2% of patients still experience significant night glare which seriously
interferes with their night driving. Severe night glare can reduce vision in all
reduced lighting conditions producing blurriness, ghosting or haloes. Patients
with large pupils and severe myopia are at greatest risk for night glare.
OR LOSS OF BEST CORRECTED VISION:
Almost all patients describe
immediately following surgery. Blurriness to one degree or another is common.
With the LASIK procedure there is considerable improvement in vision within the
first 24-48 hours. Approximately 80% of the visual recovery occurs within the
first several days, with the last 20% of vision improving over 3-6 months.
Patients experience a large quantitative jump in vision within days, with the
qualitative "fine tuning" or sharpness of vision taking much longer,
in the order of several weeks. Many patients do experience a profound and
dramatic visual improvement and become able to read half or more of the eye
chart the next day, but most state it is still not clear and crisp, and has been
described as "Vaseline Vision".
Approximately, 1-2% of patients independent of the
procedure performed will develop corneal irregularities reducing the sharpness,
crispness, and clarity of their vision preventing them form reading the bottom 2
or more lines on an eye chart that glasses, contacts or another surgery cannot
restore. That is, the initial blurriness resolves in 98-99% of patients over
however it may be permanent in 1-2% of treated
patients. There is
no way of predicting or predetermining who will be in this 1-2%. A patient that
loses sharpness, will have vision that is permanently worse. All forms of eye
surgeries alter human tissue and possess some risk.
refers to the tendency of the eye to bounce back somewhat towards your original
prescription following Laser Vision Correction. If your vision regresses, you
may require an enhancement procedure or a thin pair of glasses. In
most cases, the regression experienced is minimal and is accounted for when
planning your procedure. In some cases, glasses for night driving may be all
that is required by a patient who experiences regression.
It is essential that you
understand as much as possible about the risks associated with the excimer laser
procedure. The risk of having a serious vision-threatening complication is much
less than 1%, however, the excimer laser procedure, like all surgical
procedures, has limitations and risks.
CORNEAL FLAP COMPLICATIONS:
The entire incision time is approximately 2 seconds, but during this brief
interval a lot of things need to go right. The overwhelming majority of LASIK
complications are related to the creation of the corneal flap. Primarily, there
must be adequate internal suction pressure within the eye. Suction pressure and
microkeratome assembly and function determine the thickness of the corneal flap
of tissue. There is a 1% risk that the eye will experience a corneal flap
complication. The primary result of inadequate suction pressure is a corneal
flap that is too thin which may result in (1) postponing the procedure for three
months; permanent blurred vision. Other potential flap complications include a
corneal flap incision which is too long, resulting in a free flap, this may
increase the potential for prolonged visual recovery, blurred vision and
epithelial ingrowth (discussed below). Corneal flap incisions which are too
short necessitate postponing surgery for three months. The most dangerous risk
is if the incision goes too deep, this may result in perforation of the eye and
immediate blindness. There is a plate in the microkeratome that prevents the
incision from perforating the eye. The plate and microkeratome assembly is
checked before each and every procedure and the unit tested for proper
Prolonged Surface Healing:
During the LASIK surgery, the corneal surface is essentially left intact on the
flap. Sometimes the outer layer of cells is not sufficiently attached to the
underlying tissue. When this is so, the process of using the microkeratome may
remove a small portion of the outer cell layer. This will cause pain in the
post-operative period for up to two days as the cornea heals. This condition
responds well to either patching the eye or using a soft contact lens as a
bandage, along with additional pain medication. Visual acuity will be reduced
during the healing process.
During the first 24 hours the epithelial protective layer grows over the corneal
flap. There is a 2% risk that epithelial cells may grow underneath the flap.
This is more common in people with weak protective layers which bond poorly to
the eye surface. Any intra-operative breakdown of the protective layer may
increase the incidence of epithelial ingrowth. Treatment involves lifting the
flap and clearing the cells. Untreated epithelial ingrowth may distort vision
and may actually damage the flap if severe and progressive. Small ingrowths do
not usually present any visual problems and need only be monitored.
1% of patients develop significant complications (note, this goes up significantly
higher in surgeons who are in their learning curve).
NO ONE ever believes they will
be in the 1% of people who have complications. LASIK performed for severe myopia
and astigmatism is associated with a higher risk of complications; approximately
2%. No one has ever gone blind from Excimer laser surgery BUT you could be the
There are no guarantees of perfect vision. There are no
guarantees of zero glasses or contacts. There are no guarantees that you will
not be in the 1% of people that have significant complications. LASIK carries a
higher risk of perforation and blindness than PRK, but a lower risk of pain,
infection, scarring with faster recovery and less need for eye drops. LASIK
carries a higher risk of intra-operative complications and lower post-operative
The goal of the procedure is to achieve the best visual result in the safest
way. The goal is NOT to eliminate glasses and contacts completely but to
dramatically reduce the dependence upon them. Night driving glasses and readers
may always be needed even with a successful procedure.
The degree of correction required determines both the
rate of recovery and the initial accuracy of the procedure. Severe prescriptions
require at least two procedures. Patient differences in healing will also
greatly affect visual recovery and final visual outcome and is impossible to
As discussed, even 90% clarity of vision is 10% blurry. Enhancement surgeries
can be performed when vision is stable UNLESS it is unwise or unsafe. Typically
if -1.00 diopter or greater correction remains or vision is 20/40 or worse, an
enhancement may be performed. Enhancement surgeries are generally performed no
sooner than 3 months after the first surgery. Generally, at this point there is
no need to make another cut with the microkeratome, the original flap can
usually be lifted with specialized techniques. After 6 months of healing, a new
LASIK incision is usually required, incurring a greater risk.
In order to perform an enhancement surgery, there must
be adequate tissue remaining. If there is inadequate tissue, it may not be
possible to perform an enhancement. An assessment and consultation will be held
with the surgeon at which time the benefits and risks of an enhancement surgery
will be discussed.
IMPROVEMENT OF VISUAL
Patients who do not see 20/20 or 100% before surgery even with the strongest
prescription cannot expect to anticipate 100% after surgery. That is, after the
best vision a patient can attain is the vision they experienced per-operatively
with their correction. This surgery does not improve visual potential.
Everyone over the age of 40 will eventually experience presbyopia, resulting in
the need for reading glasses or bifocals. In monovision the aim is to have the
non-dominant eye a little under-corrected to help reading vision. This involves
giving up a little distance sharpness. Night driving glasses are more common and
readers may still be required for fine print or prolonged reading BUT overall
dependence is still dramatically reduced. Monovision helps with simple near
tasks such as opening mail reading price tags, or looking at one’s watch.
Patients who desire the best distance vision unaided should avoid monovision.