Slit-lamp exam

Alternative names


The slit-lamp examination looks at structures that are at the front of the eye (the anterior segment): The eyelid, the sclera (white outer structure of the eye), conjunctiva (membranes lining the eyelid and sclera surface), iris (colored part of the eye), natural crystalline lens, and the cornea (thin transparent membrane that covers the iris and the lens).

The slit-lamp is an instrument used with a high-intensity light source that can be focused to shine as a slit. It is used with the biomicroscope (an optical instrument that is like a microscope with two eyepieces).

How the test is performed

While you are seated in the examining chair, the instrument is placed in front of you and you rest your chin and forehead on a support to keep your head steady. Your eyes are then examined through the biomicroscope. A fine strip of paper that is stained with an orange-colored dye (fluorescein) may be touched to the side of your eye. The dye stains the tear film on the surface of the eye to help with the examination. The dye rinses out of the eye with tears.

After this examination, drops may be placed in your eyes to dilate the pupils. The drops take about 15 to 20 minutes to work. The examination is then repeated, allowing the back of the eye to be examined.

How to prepare for the test
No special preparation is necessary for this test.

The physical and psychological preparation you can provide for this or any test or procedure depends on your child’s age, interests, previous experiences, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child’s age:

  • Toddler test or procedure preparation (1 to 3 years)  
  • Preschooler test or procedure preparation (3 to 6 years)  
  • Schoolage test or procedure preparation (6 to 12 years)  
  • Adolescent test or procedure preparation (12 to 18 years)

How the test will feel

There will be light sensitivity for a few hours after the exam if dilating drops are used.

Why the test is performed
The test is used to examine the eyelids, sclera, lens, conjunctiva, iris, and cornea.

Normal Values
Structures in the eye are found to be normal.

What abnormal results mean

The slit lamp exam may detect many diseases of the eye, including:

  • Cataract  
  • Corneal injury  
  • Macular degeneration  
  • Presbyopia  
  • Retinal detachment  
  • Retinal vessel occlusion  
  • Retinitis pigmentosa  
  • Sjogren syndrome  
  • uveitis

What the risks are
The dilating drops may cause increased pressure in the eye with nausea and pain. This is very rare, but you should IMMEDIATELY return to your doctor’s office if you experience either of these symptoms.

Johns Hopkins patient information

Last revised: December 3, 2012
by Gevorg A. Poghosian, Ph.D.

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