The slit lamp is a special microscope that
is used to look into the eye. It provides a magnified, three-dimensional view
of the structures within the eye. Using the slit lamp alone, the health
professional can examine the front (anterior) chamber of the eye. Special
lenses can be used to view deeper structures of the eye, such as the
drainage angle and the optic nerve, located in the
back of the eye.
If pressure in the eyes is going to be measured
(tonometry) during the slit lamp exam, a drop or two of a special dye may be
put into the eye. Anesthetic drops also are used to numb the clear covering
(cornea) over the iris, the colored part of the eye.
This dye is quickly absorbed into the tears. It does not stain the eye unless
you have damaged cells in the outer surface of the cornea. Other drops may be
used to make the opening (pupil) in the center of the eye bigger, making it
easier to see the structures in the back of the eye, such as the optic
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Dim light might make it difficult for the eyes to focus, which can cause
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Primary care doctors or
ophthalmologists often use the slit lamp to carefully
examine the structures of the eye.
Why It Is Done
A slit lamp exam is often used as
part of a routine eye exam. It is used to detect disorders in the front of the
eye, such as clouding of the lens (cataracts), glaucoma, or abnormalities of
the cornea. When a special lens is used, the slit lamp can also give
information about structures in the back of the eye, such as the optic
With the slit lamp, the
doctor can identify thinning of the nerve tissue, which may be a sign of
What To Think About
Tonometry and gonioscopy can be
done using a slit lamp and may be part of a slit lamp exam. See tonometry and
gonioscopy in the Exams and Tests section of the topic Glaucoma.