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
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.
Fluorescein dye 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
Routine 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:
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
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?).
Most of the time, a slit lamp
examination is done by an
optometrist. In some situations, a
family medicine doctor or an
emergency medicine specialist may perform the
A test called fluorescein staining may be done along with
a slit lamp examination.
A slit lamp examination takes about 5 to 10 minutes.
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.
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.
The slit lamp exam uses an instrument that
provides a magnified, three-dimensional (3-D) view of the different parts of
The inability to remain still
throughout a slit lamp examination may make it hard for your doctor to check
Other Works Consulted
Chernecky CC, Berger BJ (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis:
January 9, 2013
Kathleen Romito, MD - Family Medicine
& Christopher J. Rudnisky, MD, MPH, FRCSC - Ophthalmology
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