The risks outlined below apply
to both PRK and LASIK procedures. The chances of having a serious
vision-threatening complication are minimal, and there have been
no reported cases of blindness following either PRK or LASIK,
says James Salz, M.D., clinical professor of ophthalmology. However,
FDA is aware of a few instances of severe eye injury requiring
corneal transplant.
Infection
and delayed healing: There
is about a 0.1 percent chance of the cornea becoming infected
after PRK, and a somewhat smaller chance after LASIK. Generally,
this means added discomfort and a delay in healing, with no long-term
effects within a period of four years.
Undercorrection/Overcorrection:
It is not possible
to predict perfectly how your eye will respond to laser surgery.
As a result, you may still need corrective lenses after the procedure
to obtain good vision. In some cases, a second procedure can
be done to improve the result.
Decrease
in Best-Corrected Vision: After
refractive surgery, some patients find that their best obtainable
vision with corrective lenses is worse than it was before the
surgery. This can occur as a result of irregular tissue removal
or the development of corneal haze.
Excessive
Corneal Haze: Corneal
haze occurs as part of the normal healing process after PRK.
In most cases, it has little or no effect on the final vision
and can only be seen by an eye doctor with a microscope. However,
there are some cases of excessive haze that interferes with vision.
As with undercorrections, this can often be dealt with by means
of an additional laser treatment. The risk of significant haze
is much less
with LASIK than with PRK.
Regression: In some patients the effect of refractive
surgery is gradually lost over several months. This is like an
undercorrection, and a re-treatment is often feasible.
Halo Effect:
The halo effect is
an optical effect that is noticed in dim light. As the pupil
enlarges, a second faded image is produced by the untreated peripheral
cornea. For some patients who have undergone PRK or LASIK, this
effect can interfere with night driving.
Flap Damage
or Loss (LASIK only): Instead
of creating a hinged flap of tissue on the central cornea, the
entire flap could come off. If this were to occur it could be
replaced after the laser treatment. However, there is a risk
that the flap could be damaged or lost.
Distorted
Flap (LASIK only):
Irregular healing of the corneal flap could create a distorted
corneal shape, resulting in a decrease of best-corrected vision.
Incomplete
Procedure: Equipment
malfunction may require the procedure to be stopped before completion.
This is a more significant factor in LASIK, with its higher degree
of complexity, than in PRK.
Problems
with a Perfect Procedure:
Even when everything goes perfectly, there are effects that might
cause some dissatisfaction. Older patients should be aware that
they can't have both good distance vision and good near vision
in the same eye without corrective lenses. Some myopic patients
rely on their myopia (by taking off their glasses, or by wearing
a weaker prescription) to allow them to read. Such a patient
may need reading glasses after the myopia is surgically corrected.
Another consideration is the delay between eye treatments. If
one eye is being done at a time, then the eyes may not work well
together during the time between treatments. If a contact lens
is not tolerated on the unoperated eye, work and driving may
be awkward or impossible until the second eye has been treated.
