How It Is Done

Most of the time, a slit lamp examination is done by an ophthalmologist or optometrist. In some situations, a family medicine doctor or an emergency medicine specialist may perform the test.

The doctor may put one or more types of drops in your eye. Dilating drops may be used to make the opening (pupil) in the center of the eye bigger. This makes it easier for the doctor to see the structures of your eye. Anesthetic eyedrops may be used to numb your eye if a foreign body is to be removed or if eye pressure is being measured (tonometry). In some cases, fluorescein dye is used.

You will sit in a chair and rest your chin and forehead against bars on the slit lamp. The lights in the room will be dimmed.

The slit lamp will be placed in front of your eyes, in line with the doctor's eyes. Focus your eyes in the direction requested by the doctor and try to hold your eyes steady without blinking.

A narrow beam of bright light from the slit lamp is directed into your eye while the doctor looks through the microscope. In some cases, a camera may be attached to the slit lamp to take photographs of different parts of the eye.

A test called fluorescein staining may be done along with a slit lamp examination.

During this test, your doctor applies a dye called fluorescein as an eyedrop or as a paper strip that is gently touched to the inside of your lower eyelid. The dye dissolves in your tears, coats your cornea, and collects temporarily in any scratches or other abnormal areas. The rest of the dye is washed away by your tears.

Your doctor shines a light onto your eye. The fluorescein dye shows up under the light, allowing the doctor to see scratches, ulcers, burns, or areas of irritation from an infection or dryness.

A slit lamp examination takes about 5 to 10 minutes.