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
Why It Is Done
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:
- 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,
conjunctivitis , or
- To help detect and monitor
- 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
- To monitor complications such as bleeding
after an eye injury.
- To monitor complications such as cataract
formation that occur because of
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
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?).