Laser Risks
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 one percent, however, the excimer laser procedure, like all surgical procedures, has limitations and risks.
In general, most of the risks following the LASIK and PRK procedures are the same. However, while LASIK does offer a faster and easier visual recovery, it also has specific risks due to the creation of the corneal flap.
Refractive
Complications
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 overcorrections and undercorrections 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 overcorrection: one in 100
Incidence of significant undercorrection: varies with
prescription
Infection
This is probably the greatest risk during the first 48 to 72 hours following the
procedure. You will receive antibiotic drops, both before and after the
procedure, to help prevent an infection. Most minor infections are treated and
quickly eliminated.
Incidence of
serious infection: one in 5000 for LASIK, one in
1000 for PRK
Post-Treatment Haze
Healing haze is the term for the collagen protein that develops on the surface
of your eye following the procedure. Almost everyone develops trace degrees of
haze. It is invisible to the naked eye
and very rarely affects your vision. Most patients are not even aware that they
have haze. Although treatable in most cases, haze usually clears gradually over
many months following the procedure.
Incidence of serious haze: one in 1000 for LASIK, one in 100 for PRK
Regression
Regression 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.
Night Glare
Even before having laser vision correction, many people experience poor night
vision or night glare (haloes, starbursting) when wearing glasses or contact
lenses. Night glare is common immediately following the procedure and will
typically last for three or four months. By the time both your eyes are treated
or six months have passed, your night glare tends to decrease and you should be
back to where you began. However, you may still require glasses for driving at
night.
Incidence of
significant glare: one in 50
Post-Treatment
Discomfort
You will not have any pain or discomfort during the laser procedure itself. With
new techniques, a relatively small number of patients experience discomfort
following the procedure, which can usually be easily treated with medication.
Most patients experience some irritation, sensitivity to light, and watering or
swelling of their eyes for a few days following the procedure.
Incidence:
one in 50 for LASIK, one in 10 for PRK
Loss of Best
Corrected Vision
A small number of patients experience a slight loss of visual sharpness or
crispness following laser vision correction (compared to when they were wearing
glasses before the procedure). If this occurs, you will lose the ability to read
the bottom one to three lines of the eye chart. In some cases, the sharpness
returns over a period of six to 12 months. This means that after the procedure,
even with glasses or contact lenses, you may not be able to see as clearly as
you did prior to the procedure.
Incidence:
one in 100
In a few instances, patients will actually gain sharpness of vision, meaning that their vision following the procedure is better than their best-corrected vision before the procedure.
LASIK Flap
Complications
While only about 1 percent of patients have complications with their LASIK
procedure, even fewer experience a serious flap-related complication. This may
result in loss of best-corrected vision.
Incidence:
one in 500
Corneal Flap
Complications
The primary benefits of LASIK are related to the creation of the protective
corneal flap. The corneal flap must be of clinically adequate quality, thickness
and size to proceed with laser treatment. Corneal flap complications range in
severity from those that simply require the procedure to be postponed by three
to six months, to those that create permanent corneal irregularities resulting
in blurred vision. The most severe LASIK complication is that of corneal
perforation, which has been reported several dozen times worldwide. Corneal flap
complications that occur after the LASIK procedure during the recovery period
include displacement and wrinkling of the corneal flap and epithelial in-growth.
Corneal flap problems include but are not limited to:
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Corneal flaps of inadequate size, typically too short, preventing laser treatment, and requiring the LASIK procedure to be repeated in three to six months. Typically no serious visual disturbance although glare and shadowing may occasionally be produced.
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Corneal flaps of inadequate thickness, may or may not be adequate for laser treatment, and may result in the procedure being stopped and repeated after three to six months. A thin corneal flap may result in a slow visual recovery over weeks to months and possibly permanently blurred vision with or without laser treatment.
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Corneal flaps of inadequate quality or smoothness include a variety of corneal flap problems, which may produce serious permanent corneal irregularities and significant visual blurring. Corneal flap irregularities may be produced because of inadequate suction pressure, inadequate orbital size, inadequate patient cooperation, malfunction or problems with the microkeratome, blade or suction apparatus.
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Corneal flaps are routinely hinged either nasally or superiorly beneath the upper eyelid. A corneal hinge is not required for a good visual result, but a hinged corneal flap is more secure and typically heals faster and more smoothly. It is possible depending upon the corneal shape, the suction ring alignment and the microkeratome, that a free corneal cap may be produced which is not hinged to the cornea. Although the laser treatment can still be performed, if any irregularities in flap quality or thickness are noted, the corneal disc is immediately replaced and allowed to heal. If the free corneal cap is of excellent quality, then the procedure is completed, but special care must be taken during the first 24 to 48 hours not to displace or lose the corneal cap. Loss of the corneal cap may result in scarring, and permanent corneal irregularity and the need for more invasive surgery.
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Corneal perforation is the most serious LASIK complication. Corneal perforation is prevented by the microkeratome depth plate, which is checked before each and every procedure. Some microkeratomes have fixed corneal depth plates. Perforation of the cornea requires corneal suturing, and the need for an intraocular lens implant as the natural lens is usually lost or damaged. It should be appreciated that corneal perforation may also potentially result in infection, the need for a corneal transplant or even rarely blindness.
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Corneal flap displacement, partial or complete, occurs during the early post-operative period, typically during the first 12 to 24 hours, but may occur days to weeks later with trauma. Care should be taken to protect the eyes from trauma, as well as avoiding rubbing the eyes or forcefully closing the eyes during the first week following LASIK. Partial displacement of the corneal flap may result in corneal striae or wrinkles, which blurs vision both qualitatively and quantitatively. Most corneal striae are treatable but some may be resistant to treatment, especially in highly nearsighted patients. Complete displacement of the corneal flap is often painful and requires urgent replacement. There is a higher risk of epithelial in-growth and infection with corneal flap displacement.
Epithelial
In-growth
Epithelial in-growth occurs during the first month following LASIK and is more
likely to occur in patients with an abnormal or weakly adherent protective
layer, for which age is a factor. Epithelial in-growth is produced when
epithelial surface cells grow underneath the corneal flap during the healing of
the corneal flap incision. Epithelial in-growth is more common with any trauma
or breakdown of the epithelium, which is more common in LASIK enhancement
procedures and long-term contact lens wearers. Treatment of this condition
involves lifting the flap and clearing the cells away. Although most small areas
of epithelial in-growth need only be monitored, untreated large areas of
epithelial in-growth may distort vision and may actually damage the flap
integrity if severe and progressive.
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