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What
are the risks involved with LASIK?
LASIK
is a surgical procedure, and like all surgeries, it possesses the
potential for risks and complications. The
following information provides you with an understanding of the
risks so you can make an informed decision.
In
spite of our best efforts, an all inclusive list or discussion of
any and all possible complications and risks is beyond the scope
of this web site, and should be discussed with your Surgeon.
Presbyopia
While
not strictly a complication, patients who are nearing or older that
forty years of age need to be aware of a change in their vision
after Lasik. If the patient is nearsighted (able to read comfortably
without glasses, but unable to see clearly in the distance without
glasses), Lasik surgery is intended to correct the vision for clear
sight in the distance (driving, watching a movie, most sports),
but once the surgery is performed reading without glasses will almost
certainly become more difficult. The patient, in contrast to vision
prior to lasik, will need reading glasses ("magnifiers", "granny
glasses", "half eyes") for close up work, or activities. This would
include reading, possibly computer work, even something as simple
as telling time on a watch. This concept is so important that your
doctor should demonstrate this to you by putting distance contacts
on to simulate post Lasik vision. This is not an issue for patients
usually under forty. These patients will be able to 'accommodate"
or "focus" on close up objects. However, they too will encounter
"presbyopia" in their early forties. Patients who are having purely
hyperopic correction or astigmatic correction are not as affected
by this concern. If you do not understand this completely, have
one of our staff, or the Doctor review this with you
Expectations
Again,
this is not strictly a complication, but a fact that must be addressed.
No one can promise "perfect vision", or even 20/20 vision.
The goal of laser vision correction is to achieve the best possible
vision without any compromise to your safety. The goal is to improve
your vision, reducing your need for glasses or contacts, to improve
your quality of life. You may find that glasses will be helpful
for driving at night, and the issue of reading glasses has already
been addressed. As a practical guide, most laser pateients no longer
require glasses for driving, sports, or watching a movie. If
you are in any way unsure of what your expectations from surgery
are, please discuss this with your surgeon.
Corneal
Haze
Numerous studies demonstrate that the incidence of corneal haze
is significantly lower with LASIK than with PRK. Corneal haze –
what the doctor sees under the slit lamp – results from the
superficial cornea's healing reaction after contact with a laser.
An ophthalmologist can measure the haze response of a patient's
cornea under a slit lamp, but patients' experiences of haze vary.
Corneal haze may not affect the patient's vision at all, but if
severe, can cause loss of best corrected visual acuity. Corneal
haze often decreases with time. The larger studies we cite do not
note the incidence of corneal haze as a statistically significant
complication of LASIK.
Decreased Night or Low-Light Vision
Corneal haze should not be confused with "hazy vision"
that some patients may experience at night or in dim light. Decreased
night or low-light vision is characterized by symptoms such as glare,
halos and starbursts that are seen around objects at night or in
dim-light conditions. Although these symptoms do not necessarily
interfere with visual acuity as it is measured by an eye chart,
for some patients, the experience can interfere with daily activities
and driving at night.
No
major study has cited the complication incidence of decreased night
vision in LASIK, and a good deal of debate exists about how common
the complication is. Dr. George O. Waring III recently estimated
that about 10% of patients experience temporary problems with decreased
night vision, representing a moderate estimate. These symptoms,
along with dry eyes and vision that gets progressively blurrier
during the day immediately following LASIK, have been termed the
"LASIK Triad" by Dr. Daniel Durrie. These symptoms subside
within one month to 6 months for the vast majority of patients who
experience them, although some will continue to experience these
symptoms for a greater length of time.
These
studies and others suggest that by softening the angle of ablation
at the periphery of the ablation zone using a multi-zone technique
and by controlling the ablation depth, surgeons can significantly
reduce the incidence of diminished night vision. As more and more
surgeons adopt the recommendations these studies suggest, we can
expect the incidence of these complications to decrease.
There
appears to be a correlation between wide pupils and the experience
of decreased night or low-light vision. Patients who have wide pupils
are more likely to experience decreased night vision following LASI
than the general population. The maximum ablation zone labeled for
treatment of nearsightedness in the US is 6.5mm and the maximum
labeled for treatment of farsightedness is 9mm. Those patients whose
pupils widen to greater than these zones in dim light need to carefully
weigh the increased risk posed to their vision. Dr. Jonathan Davidorf's
letter regarding measurement of pupil size underscores the importance
of this issue.
However,
not everyone with wide pupils will experience decreased night vision.
Currently, it is impossible to determine in advance who will experience
the complication and who will not.
Those
patients who experience persistent glare, halos or starbursts do
have several treatment options, including prescription eye drops
to help constrict the pupil at night to reduce the symptoms of decreased
night vision. However, this pharmaceutical approach is not successful
for all people, and it also can represent a significant expense
over time. Similarly, enhancement procedures may be an option, but
not everyone is eligible for an additional procedure. Eligibility
for enhancements depends on a number of factors that a doctor must
evaluate.
Severe
Dry Eye
As more experience is gained with longer term follow-up of past
operative Lasik patients it has become clear that post surgical
dry eye is a significant concern. This is thought to be due to several
factors. lasik, with the formation of a corneal flap, will necessarily
sever nerve endings on the cornea. This leads to a relative lack
of sensation on the cornea, and interference with the normal stimulus
for tearing. The nerves gradually regenerate, but this may take
several months. It is also possible that the application of the
suction ring can cause some damage to limbal goblet cells, altering
normal tear physiologyu. During the post operative period, many
patients will need to use tear supplements, punctal occlusion, and
in some cases nutritional changes can be helpful.
Dr.
Robert Maloney reported the results of a survey of 550 patients
after LASIK. Forty to fifty percent noted experiencing dry eyes
at some time of the day 3 months post-operatively. Dr. Richard Lindstrom
noted that while the overall frequency of complications after LASIK
is decreasing, the incidence of dry eye after LASIK is increasing.
Dr. Roger Steinert supported Dr. Lindstrom's assertion and provided
a possible explanation: patients seek LASIK precisely because they
are contact lens intolerant. Such intolerance is often indicative
of dry eye.
Dr.
Marguerite McDonald noted several other possible explanations for
the increased frequency of this condition post-operatively:
Use
of post-operative steroids after LASIK may exacerbate pre-existing
dry eye. Previous contact lens wear disrupts normal corneal physiology.
Hormonal changes during menopause or birth control pills can cause
dry eye. The surgery itself may cause dry eye by cutting the nerves
of the central cornea or damaging cilia.
Suggestions
for treatment included:
Post-operative
treatment with unpreserved artificial tears at least every 2 hours.
Inserting punctal plugs in cases of severe dry eye postoperatively.
All
patients should be aware that dry eye is a potential complication
of LASIK. Additionally, patients who seek LASIK who have suffered
from dry eye before, are bothered by contact lenses, are going through
menopause or taking birth control pills should be certain to have
a good conversation with their doctor about the potential for increased
risk.
Ophthalmic
literature delineates two kinds of complications: intra-operative
complications ("surgical" complications that occur during
the procedure itself) and post-operative complications ("healing"
complications that arise after the procedure has been completed).
Intraoperative
Complications
The primary intraoperative complications are related to problems
with creation of the flap (too small, too large, off center, too
thin, lost, irregular or damaged flaps.
Intra-operative
Complications Noted in Selected Studies
Complication
Rate
CRS-USA LASIK Study (n=1800)
1.2%
Emory Study (n=1,062)
1.8%
Lin & Maloney (n=1,019)
2.2%
As
of April 1, 1998, the CRS-USA LASIK Study that considered 1,800
eyes noted two complications that arose during the procedures themselves
resulting from the microkeratome: irregular cuts damaging the stromal
bed (experienced by 0.03% of the patient population) and damage
to the epithelium (0.47%). Two complications required patients to
forgo treatment or return another day but did not cause loss of
visual acuity: flaps were too small (0.38%) or too thin (0.38%).
All of the aforementioned complications produced temporary effects.
After 3 months, the visual results of the group experiencing Intra-operative
complications were no different from the group who experienced no
such complications.4
In
January, 1999, the results of the Emory Study that considered 1062
eyes and 1530 surgical procedures were published. The study noted
a 1.8% intra-operative complication rate. Seventeen eyes had to
forgo treatment that day due to flap complications. Only 3 eyes
lost 2 or more Snellen lines of best corrected visual acuity (BCVA).5
A study
conducted by Doctors Robert Lin and Robert K. Maloney that considered
1,019 eyes for which a flap was created by means of a microkeratome
noted a 2.2% intra-operative complication rate. However, no eyes
suffered permanent decrease in visual acuity because of flap complications.6
Post-operative
Complications (Healing)
The
primary post operative complications to be considered are flap irregularities,
stria, interface inflammation or infection and epithelial ingrowth.
While significant and sometimes serious, most can be corrected with
appropriate diagnosis and management.
The CRS-USA LASIK Study noted that overall, 5.8% of LASIK patients
experienced complications at the three-month follow up period that
did not result from complications during the procedure itself. Thes
complications included corneal edema (0.6%), corneal scarring (0.1%),
persistent epithelial defect (0.5%), significant glare (0.2%), persistent
discomfort or pain (0.5%), interface epithelium (0.6%), cap thinning
(0.1%) and interface debris (3.2%). It is important to note that
interface debris – retained metallic particles, lint, etc.
under the flap – almost always causes no harm to the health
or vision of the eye. None of these complications resulted in a
loss of two or more lines of BCVA, and there was no incidence of
infection amongst the study population.
The
Emory Study observed complications in 2.6% of all procedures post-operatively.
Cap dislocation occurred in 0.8% of cases, but all caps were repositioned
within 2 days after surgery with loss of one or no lines BCVA. Epithelial
ingrowth occurred in 9.1% of eyes but was not associated with loss
of BCVA. Only one eye lost 2 or more lines of BCVA, and this eye
had post-operative flap folds. There was no incidence of infection
amongst the study population. A study of 598 eyes by Knorz et al
noted post-operative complications were observed in 0.9% of cases.
Peripheral epithelial ingrowth occurred in 4 cases, and 2 eyes lost
2 or more lines of best corrected visual acuity.7
Acuity
In addition, CRS broke out 754 eyes that were not treated for astigmatism.
None lost two or more lines of BCVA. One hundred six of these patients
reported having lost between one and two lines of vision at some
point during th 3 months between the operation and the post-operative
visit. Of the 106, 69 had regained BCVA by the third month post-operatively
without the need for additional surgery. Many of the remaining 36
regained BCVA after enhancements.
Other
Risks
Every effort has been made to provide you with a good understanding
of refractive surgery, its risks, benefits and expectations. However,
this information cannot be all inclusive. Please discuss any questions
or concerns with your surgeon. We will make every effort to address
all of your issues prior to your surgery
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