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Slit Lamp Exam

What is a slit lamp exam?

Diseases of the eye can be difficult to diagnose during a general physical examination. A doctor who specializes in treating eye problems, called an ophthalmologist, is better able to examine and diagnose these conditions because the tools they have are specific to the eyes. When you have an eye checkup, you will likely undergo a slit lamp exam.

You will usually have the slit lamp exam at an optometry or ophthalmology office. The exam is also called biomicroscopy. It allows the doctor to microscopically examine your eyes for any abnormalities or problems.

What happens during a slit lamp exam?

You do not have to prepare in advance for a slit lamp exam.

Once you are in the examination chair, the doctor will place an instrument in front of you on which to rest your chin and forehead. This helps steady your head for the exam. Your eye doctor may put drops in your eyes to make any abnormalities on the surface of your cornea more visible. The drops contain a yellow dye called fluorescein, which will wash away your tears. Additional drops may also be put in your eyes to allow your pupils to dilate, or get bigger.

The doctor will use a low-powered microscope, along with a slit lamp­, which is a high-intensity light. They will look closely at your eyes. The slit lamp has different filters to get different views of the eyes. Some doctor’s offices may have devices that capture digital images to track changes in the eyes over time.

During the test, the doctor will examine all areas of your eye, including the:

  • eyelids
  • conjunctiva
  • iris
  • lens
  • sclera
  • cornea
  • retina
  • optic nerve

The doctor will first examine the front areas of your eye and then perform the exam again with a different lens to examine the back of your eye.

What does this exam help diagnose?

A slit lamp exam can help diagnose the following conditions:

  • macular degeneration, a chronic condition affecting the part of the eye that is responsible for central vision
  • detached retina, a condition when the retina, which is an important layer of tissue at the back of the eye, becomes detached from its base
  • cataracts, a clouding of the lens that negatively affects the ability to see images clearly
  • injury to the cornea, an injury to one of the tissues that covers the surface of the eye
  • blockages of the retinal vessel, obstructions in the eye’s blood vessels that can cause a sudden or gradual loss of vision

Ask your doctor what they are looking for during the exam and which eye conditions you may be at risk for.

What to expect after the exam

Typically, there are no significant side effects of this exam. Your eyes may be sensitive to light for a while afterward, especially if your pupils were dilated. If you start feeling nauseous or have eye pain, return to your doctor’s office as soon as possible. These may be symptoms of increased pressure of the fluid in the eye, which may be a medical emergency. While the risk of this is small, the eye drops used to dilate the eye can rarely cause this to occur.

What do abnormal results mean?

If the results of your slit lamp exam are abnormal, a variety of conditions may be present, including:

  • infection
  • inflammation
  • increased pressure in the eye
  • degeneration of the arteries or veins in the eye

For example, if macular degeneration is taking place, the doctor may find drusen, which are yellow deposits that can form in the macula early on in age-related macular degeneration. If your doctor suspects a particular cause of vision problems, they may recommend further testing to get a more definitive diagnosis. 

Content licensed from:

Written by: Jaime Herndon
Medically reviewed on: Jul 07, 2016: University of Illinois-Chicago, College of Medicine

This feature is for informational purposes only and should not be used to replace the care and information received from your health care provider. Please consult a health care professional with any health concerns you may have.
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