Test Overview
The slit lamp exam uses an instrument that provides a magnified,
three-dimensional (3-D) view of the different parts of the eye. During the
exam, your doctor can look at the front parts of the eye, including the clear,
outer covering (cornea), the lens, the colored part (iris), and the front section of the gel-like 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 directly on the cornea) to view deeper structures of the
eye, such as the
optic nerve,
retina, and the area where fluid drains out of the eye
(drainage angle). A camera may be attached to the slit lamp to take photographs of
different parts of the eye.
See a picture of the
structures of the eye.
Fluorescein dye
eyedrops may be used during a slit lamp examination to make it easier to detect
a foreign body, such as a metal fragment, or an infected or injured area on the
cornea.
Why It Is Done
A slit lamp exam may be done:
- As part of a routine eye exam along with other
procedures to evaluate the eye, such as ophthalmoscopy, vision testing, or
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
detect disorders in the structures in the front of the eye, such as infection
or injury to the cornea,
cataracts,
conjunctivitis, or
iritis.
- To help detect and monitor
glaucoma or
macular degeneration.
- To check for a
foreign body, such as a metal fragment, on or in the eye.
- To detect
eye problems that may be caused by other diseases, such as
diabetes or
rheumatoid arthritis. Routine slit lamp exams are
important to detect eye problems at an early stage and to guide treatment if
eye problems develop.
- To monitor complications such as bleeding
after an eye injury.
- To monitor complications such as cataract
formation that occur because of
chemotherapy,
radiation treatment, or after a
bone marrow transplant.
How To Prepare
If you wear glasses or contact lenses,
you will need to remove them before the slit lamp examination.
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 dilating or
anesthetic eyedrops.
If dilating drops are used, your eyes may be
sensitive to light and you will have trouble focusing your eyes for several
hours. If you know your eyes will be dilated, you may wish to arrange for
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 about any concerns you have regarding 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 Done
Most of the time, a slit lamp
examination is done by an
ophthalmologist or
optometrist. In some situations, a
family medicine doctor or an
emergency medicine specialist may perform the
test.
- Your eyes may be dilated. Anesthetic eyedrops
may be used to numb your eye if a foreign body is to be removed or if eye
pressure is being measured (tonometry).
- 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
requested by the doctor and 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 photographs of
different parts of the eye. See a picture of a
slit lamp examination.
If a foreign body is present or if the cornea appears
infected or injured, a test called fluorescein staining may be done along with
a slit lamp examination.
- During this test, your health professional applies a dye called
fluorescein as 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 temporarily in any scratches or other abnormal areas. The
rest of the dye is washed away by your tears.
- Your health
professional shines a light onto your eye. The fluorescein dye shows up under
the light, allowing the health professional to see scratches, ulcers, burns, or
areas of irritation from an infection or dryness.
A slit lamp examination takes about 5 to 10 minutes.
How It Feels
There normally is no discomfort involved
with a slit lamp examination.
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 after your eyes have been dilated. Your
distance vision usually is not affected as much as your near vision, though
your eyes may be very sensitive to light. Do not drive for several hours after
your eyes have been dilated. Wearing sunglasses may make you more comfortable
until the effect of the drops wears off.
Anesthetic drops usually
wear off in about 30 minutes.
Risks
In some people, the dilating or anesthetic
eyedrops can cause:
Contact your doctor immediately if you have severe and
sudden eye pain, vision problems (halos may appear around light), or loss of
vision after the examination.
Results
The slit lamp exam uses an instrument that
provides a magnified, three-dimensional (3-D) view of the different parts of
the eye.
Slit lamp examination| Normal: | - The eyelashes, eyelids, and lining of
the eyelids (conjunctiva) look normal.
- All of the structures inside
of the eye look normal.
|
|---|
| Abnormal: | - Cataracts are
seen.
- Changes are found in the
cornea, such as an irregularly shaped cornea or a
corneal scratch (abrasion), ulcer, or infection
- A foreign body,
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.
|
|---|
What Affects the Test
The inability to remain still
throughout a slit lamp examination may make it hard for your doctor to check
your eyes.
What To Think About
- Other eye tests may be done routinely along
with a slit lamp examination, including ophthalmoscopy, vision testing, and
tonometry testing for
glaucoma. For more information, see the topics
Ophthalmoscopy,
Vision Tests, and
Tonometry.
- A test called gonioscopy may be
done during a slit lamp examination to detect certain types of glaucoma. A
special contact lens (goniolens) is placed on your eye and a narrow beam of
bright light is directed into your eye while the health professional looks
through the slit lamp at the
drainage angle in your eye. For more information, see
the topic
Gonioscopy.
- The doctor may use a
high-powered lens to examine the
vitreous gel and
retina of the eye.
References
Other Works Consulted
- Chernecky CC, Berger BJ (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis:
Saunders.
Credits
| By | Healthwise Staff |
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| Primary Medical Reviewer | Kathleen Romito, MD - Family Medicine |
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| Specialist Medical Reviewer | Christopher J. Rudnisky, MD, MPH, FRCSC - Ophthalmology |
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| Last Revised | June 9, 2011 |
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