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 nerve.

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 nerve.

Results

With the slit lamp, the doctor can identify thinning of the nerve tissue, which may be a sign of glaucoma.

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 this topic.

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