Slit Lamp Examination
Test OverviewThe slit lamp exam uses a tool that provides a magnified,
three-dimensional (3-D) view of the parts of the eye. During the
exam, your doctor can look at the front parts of the eye. These parts include the clear,
outer covering (cornea), the lens, and the colored part (iris). The doctor can also see the front part of the thick fluid
(vitreous gel) that fills the large space in the middle
of the eye. Special lenses can be placed between the slit lamp
and the cornea (or on the cornea) to help the doctor see the deeper structures of the eye. These structures include the
optic nerve,
the retina, and the area where fluid drains out of the eye
(drainage angle). A camera may be attached to the slit lamp to take pictures of
different parts of the eye. Fluorescein dye may be used during a slit lamp exam. The dye makes it easier to see
a foreign object, such as a metal fragment, or an infected or injured area on the
cornea. Why It Is DoneRoutine slit lamp exams are done to find eye problems at an early stage and to guide treatment if
eye problems develop. A slit lamp exam may be done: - As part of a routine eye exam. It may be used along with other
procedures that evaluate the eye, such as ophthalmoscopy, vision testing, and
tonometry (to measure pressure in the eye).
- To look at structures
in the back of the eye, such as the optic nerve or retina.
- To help
find problems in the structures in the front of the eye. For example, it can help find problems such as
cataracts,
conjunctivitis,
iritis, or an infection
or injury to the cornea.
- To help find and keep track of
glaucoma or
macular degeneration.
- To check for a
foreign object, such as a metal fragment, on or in the eye.
- To find
eye problems that may be caused by other diseases, such as
diabetes or
rheumatoid arthritis.
- To keep checking on problems such as bleeding
after an eye injury.
- To keep checking on problems such as cataracts that form because of
chemotherapy or
radiation treatment or after a
bone marrow transplant.
How To PrepareIf you wear glasses or contact lenses,
you will need to remove them before the slit lamp exam. Eyedrops may be used to widen (dilate) your
pupils and to numb the surface of your eyes. Before
the test, tell your doctor if you have glaucoma or are allergic to eyedrops that dilate or
numb your eyes. If dilating drops are used, your eyes may be
sensitive to light. You will have trouble focusing your eyes for several
hours. If you know your eyes will be dilated, you may wish to find
someone to drive you home after the test. You also will need to wear sunglasses
when you go outside or into a brightly lit room. Talk to your
doctor if you have any concerns about the need for the test, its risks, how it will be done, or what the results will mean. To help you understand the
importance of this test, fill out the
medical test information form(What is a PDF document?). How It Is DoneMost of the time, a slit lamp
exam is done by an
ophthalmologist or
optometrist. In some cases, a
family medicine doctor or an
emergency medicine specialist may do the
test. - The doctor may put one or more types of drops in your eye. Dilating drops may be used to make the opening (pupil) in the center of the eye bigger. This makes it easier for the doctor to see the structures of your eye. Numbing drops
may be used if a foreign object is to be removed or if eye
pressure is being checked (tonometry). In some cases, fluorescein dye is used.
- You will sit in a chair and
rest your chin and forehead against bars on the slit lamp. The lights in the
room will be dimmed.
- The slit lamp will be placed in front of your
eyes, in line with the doctor's eyes. Focus your eyes in the direction
the doctor tells you to. Try to hold your eyes steady without
blinking.
- A narrow beam of bright light from the slit lamp is
directed into your eye while the doctor looks through the microscope. In some
cases, a camera may be attached to the slit lamp to take pictures of
different parts of the eye.
A test called fluorescein staining may be done along with
a slit lamp exam. - During this test, your doctor applies a dye called
fluorescein. The dye comes in an eyedrop or as a paper strip that is gently touched to the
inside of your lower eyelid. The dye dissolves in your tears, coats your
cornea, and collects for a short time in any scratches or other abnormal areas. The
rest of the dye is washed away by your tears.
- Your doctor shines a light onto your eye. The fluorescein dye shows up under
the light. It helps the doctor to see scratches, ulcers, burns, or
areas of irritation from an infection or dryness.
A slit lamp exam takes about 5 to 10 minutes. How It FeelsIt is usually not painful to have a slit lamp test. The dilating drops may make your eyes
sting and cause a medicine taste in your mouth. You will have trouble
focusing your eyes for up to 12 hours. Your
distance vision usually is not affected as much as your near vision. But
your eyes may be very sensitive to light. Do not drive for several hours after
your eyes have been dilated, unless your doctor says it's okay. Wearing sunglasses may make you more comfortable until the effect of the drops wears off. Numbing drops usually
wear off in about 30 minutes. RisksIn some people, the dilating or numbing drops
can cause: Contact your doctor right away if you have severe and
sudden eye pain, vision problems such as halos that appear around lights, or loss of
vision after the exam. ResultsThe slit lamp exam uses a tool that
provides a magnified, three-dimensional (3-D) view of the parts of
the eye. Slit lamp exam| Normal: | - The eyelashes, eyelids, and lining of
the eyelids (conjunctiva) look normal.
- All of the structures inside
the eye look normal.
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| Abnormal: | - Cataracts are
seen.
- Changes are found in the
cornea. Examples of changes are an odd-shaped cornea, a
corneal scratch (abrasion), an ulcer, and infection.
- A foreign object,
such as a metal fragment, is found.
- Infection, such as
iritis or
conjunctivitis, is found.
- Bleeding is seen
between the
iris and cornea (hyphema) from a sudden break in a
blood vessel or as a result of an injury to the eye.
- Signs of glaucoma are seen.
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What Affects the TestNot being able to stay still
during a slit lamp exam may make it hard for your doctor to check
your eyes. What To Think About- Other eye tests may be done along
with a slit lamp exam. These tests include ophthalmoscopy, vision testing, and
tonometry testing for
glaucoma.
- A test called gonioscopy may be
done during a slit lamp exam to check for certain types of glaucoma. A
special contact lens (goniolens) is placed on your eye. A narrow beam of
bright light is pointed into your eye. Then the doctor looks
through the slit lamp at the
drainage angle in your eye. To learn more, see
the topic
Gonioscopy.
- The doctor may use a
high-powered lens to look at the
vitreous gel and
retina of the eye.
ReferencesOther Works Consulted- Chernecky CC, Berger BJ (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis: Saunders.
CreditsByHealthwise Staff
Primary Medical ReviewerKathleen Romito, MD - Family Medicine
Specialist Medical ReviewerAdam Husney, MD - Family Medicine Current as ofMay 17, 2017 Current as of:
May 17, 2017 Last modified on: 8 September 2017
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