LASIK for Myopia
(Nearsightedness) and Astigmatism
The options for correction of myopia and astigmatism now include
glasses, contact lenses, and different kinds of refractive surgery
such surface treatment by photorefractive keratectomy (PRK),
and Laser Assisted in Situ Keratomileusis (LASIK) using excimer
lasers. The goal of LASIK is to reduce your need for glasses or
contact lenses by changing the shape of the cornea through LASIK
How the Eye Functions
The cornea and lens of the eye focus light like a camera lens to
form an image on the retina at the back of the eye. The cornea,
where light first enters the front of the eye, provides about two
thirds of the eye's focusing power, and the lens inside the eye
provides the other third. Normally, in relatively young persons
(i.e., less than 50 years of age) the lens of the eye can adjust its
focusing power somewhat, so you can see objects clearly both near
and far away. The eye focuses light by refracting all light rays to
meet at a single point. If the focusing process works perfectly, a
sharp image of the object, you are looking at, will be focused
exactly on the retina and you will see a clear image. However, if
the light focuses either in front of or behind the retina, the image
on the retina (and the image you see) will be blurred, and you are
said to have a refractive error. Refractive errors are not diseases,
but are common variations observed in human beings across the world.
There are three main types of refractive error. They are called
nearsightedness (myopia), farsightedness (hyperopia) and
astigmatism. The amount of refractive error present in the eye is
measured in units called "diopters." When your eye Cannot focus
correctly, it is said to have one of the main refractive errors:
myopia or hyperopia.
Myopia usually starts in childhood and typically stabilizes in the
late teens or early adulthood. The tendency to develop myopia also
runs in families. Myopia can change from a very mild to a very
strong nearsighted effect.
Hyperopia is also very common, and is especially problematic in
older persons who have difficulty in focusing on objects up close.
Astigmatism occurs when the refractive error is stronger in a
particular direction. Astigmatism may occur with either myopia or
hyperopia. The following pictures emphasize the role of the cornea
in determining the focusing power of the eye. They show that the
more sharply the cornea is curved, the more the light rays are bent.
If the cornea is curved too much, the image focuses in front of the
retina and the eye is nearsighted. If the cornea is too flat, the
image focuses behind the retina and the eye is farsighted (Fig. 1).
When the cornea shape is just right the image from a distant object
is focused exactly on the retina.
Fig. 1: This proper focus for distance vision is
called emmetropia. Good focus depends on three factors, the overall
shape and size of your eye, the shape of the cornea, and your lens
power. During a regular eye examination, your doctor checks your
vision to determine where the eye focuses light relative to your
retina. When your doctor adjusts your vision with different lenses,
he correctly focuses light on the retina. Myopic individuals
see near objects clearly, but distant objects are blurry.
Nearsightedness and astigmatism can be corrected by any method that
reduces the total refractive power of the eye, and includes the use
of glasses, contact lenses and refractive surgery. With glasses or
contacts, changes in your vision that occur slowly over time can be
corrected by simply adjusting the lens prescription of your glasses
or contacts. Refractive surgery, on the other hand, produces changes
that are permanent.
What is LASIK?
LASIK is laser surgery to correct nearsightedness (myopia) with or
without astigmatism. An excimer laser beam is used to flatten the
middle layer of the cornea. The laser beam removes microscopic
amounts of tissue from the middle layer of the cornea, precisely
reshaping the cornea. The excimer laser produces a beam of
ultraviolet light in a series of rapid pulses. Each pulse lasts only
a few billionths of a second and removes a microscopic amount of
tissue by evaporating it (fig. 2). Excimer laser light does not
penetrate the eye and leaves other eye structures (iris, lens and
retina) undisturbed. The laser produces very little heat and is
controlled by the doctor during the operation. Prior to LASIK, some
anesthetic drops are placed on the eye to numb it. Your doctor then
begins the LASIK procedure by cutting a thin flap on the front of
the cornea using a special cutting instrument called a micro-keratome
or using a special laser machine called intralase. The doctor will
then fold back this flap of tissue much like opening a hinged
Folding back the flap will give the doctor access to the middle
layer of the cornea where the laser treatment will be performed.
This part usually takes a couple of minutes. After that, your doctor
uses the laser beam to perform the LASIK procedure. The laser
treatment usually lasts only about 10 -15 seconds. After the
laser treatment is complete, the doctor will carefully fold the flap
of cornea tissue back into place to complete the procedure.
Contraindications, Warnings & Precautions Contraindications
You should not have LASIK surgery if:
You have collagen vascular, autoimmune or immunodeficiency
diseases (for example: rheumatoid arthritis, lupus or AIDS). These
conditions may result in scarring or poor healing after LASIK
treatment resulting in reduced vision.
You are pregnant or nursing. These conditions may affect your
preoperative refraction making it difficult to choose the correct
amount of LASIK treatment.
You show signs of keratoconus (thinning of the cornea) or corneal
disease. This condition can lead to serious cornea problems that
require additional surgical repair and result in poor vision.
You have a condition which would stimulate large amounts of scar
tissue (keloid formation). Scarring can be permanent and may require
surgery to repair.
You are taking prescription medications that affect corneal
healing or your refraction. You should discuss all medications you
take, even over the- counter medications, with your eye doctor. Many
medications can affect the way your cornea is changed by the laser
and the way it heals after LASIK treatment. These may affect your
refractive outcome and possibly result in reduced vision after LASIK
Your nearsightedness is changing. If
your vision is unstable, then you should not be treated. Treatment
of unstable vision may affect the accuracy of your refractive
You have severe allergies. Your medications may have to change
before or after your eye surgery. These medications may change the
wetness (moisture level) in your eye. If the medication changes the
wetness of your eye, the accuracy of your refractive results may be
You have been diagnosed with ocular Herpes simplex or ocular
Herpes zoster. Herpes are viral infections. Laser treatment may
reactivate the infection.
You have nystagmus (uncontrolled eye movements) or another
condition that prevents a steady gaze.
You need to be able to keep
your eyes still during treatment.
Risks & Benefits
LASIK is a laser surgical procedure involving your eyes and has some
risks. You should consider and discuss with your doctor the risks
that are noted here. These are based on clinical experience with
LASIK cases and the possibilities that doctors believe should be
considered for this kind of eye surgery.
At the time of surgery, it is possible that the flap will not be
cut correctly. In some cases, the flap of tissue may not be the
correct size or shape or may be too thin. In these cases, the doctor
may have to stop the surgery, fold the flap into position, and allow
it to heal. In most cases, the doctor can complete surgery at a
later date. In the studies on LASIK, the majorities of these cases
were completed later and had a successful result.
Although the effects of LASIK on visual performance under poor
lighting conditions have not been determined, it is possible that
you will find it more difficult than usual to see in conditions such
as very dim light, rain, snow, fog or glare from bright lights at
night. These effects have been reported as being more common in
persons with large pupils (over 6 mm). It is possible that these may
be permanent effects.
The first week following surgery: The following complications have
been reported up to several weeks following LASIK treatment. They
are associated with the normal healing process after treatment and
Discomfort, pressure feeling, scratchiness, burning sensation,
and dryness may last for up to 1 day after surgery, for which your
eye doctor can provide medications.
feeling that something is in your eye.
Swelling of the cornea.
problem with healing of the corneal flap, including damage to the
flap, loss or misalignment of the flap, or growth of cornea surface
cells under the flap. If needed, the doctor may lift the flap to
clean the middle layer of the cornea and reposition the flap to
vision and tearing or watery eyes may occur as the cornea and the
flap heals in the first few hours.
Sensitivity to bright lights may occur in first few hours.
The first two or six months following
intraocular pressure may increase due to use of steroid or
anti-inflammatory medications (0% to 0.1% of eyes had a significant
elevation in intraocular pressure in this time frame). This is
usually resolved by drug therapy or by stopping the use of steroid
or anti-inflammatory medication.
cloudy vision rarely occurs after LASIK surgery (<1.0% of eyes had
mild or moderate haze with no significant loss of vision).
in fluctuation of vision (40.0% pre-operatively vs. 64.3% post
pre-operatively vs. 35.7% post-operatively).
You should contact your doctor if you notice any pain or change or
loss of vision in the eye. Eye pain or sudden loss of vision can
indicate a serious problem that required immediate medical
One year after surgery: At one year
after LASIK surgery the following vision-threatening events
a significant amount (more than 2 lines lost on an eye chart) of
vision even with glasses.(0.6%)
3. If the
results of the surgery are not satisfactory, you many need to have
additional LASIK surgery in the same eye.
surgery is effective in reducing nearsightedness requiring
correction from -1.00 to -11.00 diopters spherical equivalent in
patients with 0.00 to -4.00 diopters of astigmatism.
may reduce overall nearsightedness (95% significantly improved
uncorrected vision to the level of 20/40 or better at 6 months).
may reduce or eliminate dependency upon contact lenses or glasses (>
90% could see 20/20 or better without glasses or contacts at 6
should be considered a permanent surgical procedure, in that the
refractive result changes little after the first few months. If your
refractive result is unsatisfactory, your doctor may recommend
further surgical treatments, or correcting your remaining refractive
error with glasses or contacts.
Are you a good candidate for LASIK?
are considering LASIK you must:
least > 18 years of age.
healthy eyes which are free from eye disease or corneal abnormality
nearsightedness (myopia) requiring vision correction between -1.00
and -14.00 diopters spherical equivalent, with 0.00 to -4.00
diopters of astigmatism.
your eye doctor has satisfactory evidence that your refraction has
been stable over the past year (changed by less than or equal to 0.5 diopters in your vision correction, or by less than or equal to 0.5
diopters in your astigmatism correction).
informed of LASIK risks and benefits as compared to other available
treatments for nearsightedness (myopia) and astigmatism.
willing to sign an informed consent form, as provided by your eye
Summary of Important Information
is a permanent operation to the cornea that cannot be easily
Alternatives to LASIK include glasses, contact lenses, PRK.
is not a laser version of radial keratotomy (RK); they are
completely different from one another.
occupations, such as pilots, do not accept applicants who have had
any refractive surgery.
Refractive error must be stable (within ±0.5 diopters in your vision
correction, or within ±0.5 diopters in your astigmatism correction)
for at least one year before surgery.
The following risks of LASIK surgery
should be noted:
Temporary discomfort may be expected for 24-72 hours after surgery.
If the discomfort persists, please contact your doctor.
Problems that may last several days: corneal swelling, blurred
vision, feeling something in the eye, shadow images, light
sensitivity, tearing, and pupil enlargement.
Adverse events beyond the first few months: elevation of intraocular
pressure, cloudy cornea affecting vision,
overcorrection, under correction or nearsighted, loss of best vision
that can be achieved with glasses <o.1%, damaged corneal flap 1 in
800 ghost images.
The following benefits of LASIK surgery
should be noted:
Nearsightedness with astigmatism may be reduced so that the amount
of time contact lenses or glasses are used during the day is reduced
LASIK may be an alternative to glasses in some patients who are
intolerant of contact lenses.
LASIK may be another alternative to correct nearsightedness and
Patients considering LASIK surgery
(Dr. Mansoor A.
Farooqui acquired fellowship in ophthalmology from College of
Physicians and Surgeons of Pakistan (CPSP) and Fellowship of Royal
College of Surgeons of Edinburgh (FRCSED) in ophthalmlogy. His
special interests are surgeries for the removal of eye glasses. He
has done more than 6000 surgeries LASIK, PRK, Epilasik, Lasek and
Intralasik procedures. He has special certification for the verisyse
and ICL (specialized lenses to correct higher degree of refractive