Pre-operative Eye Exam
Step 3: Your pre-operative LASIK eye exam
As part of your LASIK preparation, you will need to receive a
pre-operative eye exam. If you have any questions about why a
particular test is included, please feel comfortable discussing it
with Dr. Seibel until you are satisfied with the explanation. Your
pre-operative LASIK exam will:
· Address existing eye health concerns
· Identify your potential surgical outcome
· Frame expectations for what LASIK can do
· Clarify your overall vision-health status
The pre-operative LASIK eye exam covers:
(click on any topic or scroll down)
Assessment of your eye health history
·Contact lens wear
·Ocular or systemic diseases and medications
·Previous ocular problems
·Previous eye injuries
Pre-operative LASIK eye exam
·Refraction (including dilation)
·Reviewing the results
If you are having your LASIK candidacy screening done
through a your own eye care professional, you are still required to complete
a pre-operative LASIK exam at our office before your LASIK surgery date.
We will be unable to confirm your candidacy for LASIK or PRK until these tests
Someone to drive you home
A comprehensive LASIK eye exam requires that your pupils be dilated with eye
drops. This enables us to thoroughly examine and accurately measure the eye.
The drops that are used are longer lasting than what you may be accustomed
to from past visits to the eye doctor.
These will leave your vision somewhat blurry and brighter than normal for
about four hours. We recommend that you bring a pair of dark sunglasses and a
friend or family member to drive you home afterwards. We also offer
a type of eye drop that reverses dilation (reducing the time to about one
hour), although many patients prefer not to use it because it usually causes
side effects of irritation and redness.
Assessment of your eye health history
Current prescription: Your current prescription needs to have been
stable during the last 2 years in order for LASIK to be appropriate at
Contact lens wear: Contact lenses warp the
corneal surface and lead to measurements that are not representative of your
true refraction. You will have to stop wearing contact lenses prior to LASIK
eye surgery. The time interval required depends upon the type of lens and how
long you have been wearing them, and may be longer than the minimum times listed
below depending on your initial topography results.
At least 2 weeks prior to your LASIK exam
At least 2 weeks prior to LASIK surgery
Gas permeable and true hard (PMMA) lenses
At least 3 weeks prior to your LASIK exam - if you have worn them
for more than 10 years an additional week for each decade of wear
is usually required. At least 3 weeks prior to laser eye surgery
Follow this advice in order to avoid unnecessary risk of complications
or reduce the effectiveness of your LASIK surgery.
Ocular or systemic diseases and medications: Some ocular or systemic
diseases and medications can affect your suitability as a candidate for
Previous ocular problems: This refers to such conditions as lazy
eyes, strabismus, or double vision and will need to be addressed in order
to validate your candidacy for LASIK.
Previous eye injuries: Be sure to inform Dr. Seibel about any eye
related injury, regardless of how long ago it occurred.
Your pre-operative eye exam:
Refraction: This test determines the visual acuity of your eyes,
both uncorrected and as corrected by glasses or contacts, both with and
Motility: This exam will assess the ability of the muscles to align
your eyes properly.
Eyelids: This test exams your eyelids to see if they turn inward
(possibly scratching the cornea) or outward (possibly directing tear flow
away from the eye), plus other related conditions.
Conjunctiva: The conjunctiva is the transparent membrane that covers
the outer surface of the eye and lines the inner surface of the eyelids.
This test will check for irritations, redness, irregular blood vessels
or other abnormalities.
Cornea: The cornea will be examined for overall health, scarring,
any previous trauma, and pathology, using slit lamp via a microscope.
Crystalline lens: The natural lens inside your eyes will be examined
to determine if clouding of the lens (a cataract) or other abnormalities
Intraocular pressure: The intraocular pressure inside your eye will
be measured to detect glaucoma or pre- glaucomatous conditions. Glaucoma
is a visual loss caused by damage to the optic nerve from excessively high
pressures in the eye. It is one of the most common causes of preventable
Posterior segment: The dilated (fully open) pupil exam is used to
assess the health of the posterior segment (inside back surface of your
eye). This test allows Dr. Seibel to screen the retina, optic nerve, and
blood vessels for a number of eye and systemic disorders.
Tear film: It is normal for patients to experience temporary dryness
after LASIK. However, patients who have inadequate tears before surgery
are at higher risk of prolonged dry-eye symptoms after surgery. Keep in
mind that feeling of dryness while wearing contact lenses is not the same
thing. Experiencing dry eyes while wearing contact lenses does not mean
that the eyes are dry when contact lenses are not being worn. Different methods to evaluate tear function include:
of colored agents in the tears
· Physically measuring the tears themselves
· Inspection of the tear film with a microscope
Pupil size: Most glare, halos, and diminished night-vision following LASIK
surgery is due to a combination of larger pupil size and a high amount of nearsightedness
or farsightedness. Because large pupils allow light rays to enter from the periphery of the cornea, custom programming the laser for a larger optical and ablation zone can minimize glare and halos. However, this can only be accomplished with lasers that have
an adjustable zone from 6.0 mm to 8.0 mm, such as the ones we use here at Seibel Vision Surgery.
Pupils should be measured when they are the largest potential size, which occurs
under the darkest conditions. There are four methods for pupil size evaluation:
amplification - utilizing night vision technology derived from military devices, an examiner looks through one end
of the device at the pupil. Pupil diameter is measured against a tiny ruler
the viewfinder to give accurate measurements in room light that would
otherwise be too dark to take a measurement.
Ruler card - an examiner uses a hand-held card with different sized
circles on it to match the diameter o the pupil to that of a circle on
the card. This has the disadvantage of requiring that the room lights be
bright enough for the examiner to read the card; therefore, the pupils
may be smaller with this level of illumination than they would really be
with nighttime illumination.
Visual estimation - an examiner guesses the pupil size by simply
looking at it. This is the least accurate method and has the same disadvantage
of the ruler card of requiring bright enough lighting for the examiner
to see the pupils.
Epithelium: The cornea is covered on the surface with a thin clear
layer of skin cells, called the epithelium. In some people, this layer
of cells is not attached firmly.
Loose epithelium may lead to a higher risk of complications. By microscopic
examination of the cornea, this test will determine if a loose epithelium
Corneal thickness: The medical term for measuring corneal thickness
is pachymetry. This test will be used to calculate precisely how deep the
laser will be allowed to penetrate.
Since LASIK involves creating a flap on the surface of the cornea
and using a laser to reshape the cornea by removing tissue, it is possible
for the laser to remove too much, leading to corneal bulging and distorted
vision. In order to be sure the laser does not penetrate beyond the safest
level, pachymetry is imperative.
Topography: Using a Zeiss Humphrey Atlas 995 topographer, your eyes
will be tested by corneal topography.
As no one has a perfectly rounded cornea, the topographer machine
will display the degree of astigmatism you have - the irregularities and
actual steep or flat shape of your cornea, which cause your vision to be
less than perfect. Occasionally patients have abnormal astigmatism called
keratoconus, which is a cone-shaped cornea. These corneas often are weaker
than normal corneas and thus should not be treated by LASIK.
Wavefront Mapping: The VISX CustomVue Wavefront Analyzer will provide
a detailed analysis of your entire visual system. Dr. Seibel will use this
information to further validate that you are an appropriate laser eye surgery
candidate and formulate a highly customized vision correction plan specifically
for your eyes. Read our section on Wavefront LASIK for more information
on this incredible technology.
Vocational and lifestyle: Your work or recreational requirements
can influence vision correction choices. For example, some choices can
affect depth perception or the ability to see well at a particular distance.
Reviewing the results: You and Dr. Seibel will go over the results
of your exam together and further plan your LASIK eye surgery.
Next step: Schedule and
prepare for your LASIK procedure. This
appointment will be scheduled at the time
of your comprehensive eye exam.