Slit lamp exam

Routine slit lamp exams are done to find eye problems at an early stage and to guide treatment if eye problems develop.

A slit lamp exam may be done:

• As part of a routine eye exam. It may be used along with other procedures that evaluate the eye, such as ophthalmoscopy, vision testing, and tonometry (to measure pressure in the eye).
• To look at structures in the back of the eye, such as the optic nerve or retina.
• To help find problems in the structures in the front of the eye. For example, it can help find problems such as cataracts, conjunctivitis, iritis, or an infection or injury to the cornea.
• To help find and keep track of glaucoma or macular degeneration.
• To check for a foreign object, such as a metal fragment, on or in the eye.
• To find eye problems that may be caused by other diseases, such as diabetes or rheumatoid arthritis.
• To keep checking on problems such as bleeding after an eye injury.
• To keep checking on problems such as cataracts that form because of chemotherapy or radiation treatment or after a bone marrow transplant.

Most of the time, a slit lamp exam is done by an ophthalmologist or optometrist. In some cases, a family medicine doctor or an emergency medicine specialist may do 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. Numbing drops may be used if a foreign object is to be removed or if eye pressure is being checked (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 the doctor tells you to. 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 pictures of different parts of the eye.

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

• During this test, your doctor applies a dye called fluorescein. The dye comes in 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 for a short time 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. It helps the doctor to see scratches, ulcers, burns, or areas of irritation from an infection or dryness.

A slit lamp exam takes about 5 to 10 minutes.

If you wear glasses or contact lenses, you will need to remove them before the slit lamp exam.

Eyedrops may be used to widen (dilate) your pupils and to numb the surface of your eyes. Before the test, tell your doctor if you have glaucoma or are allergic to eyedrops that dilate or numb your eyes.

If dilating drops are used, your eyes may be sensitive to light. You will have trouble focusing your eyes for several hours. If you know that your eyes will be dilated, you may wish to find someone to drive you home after the test. You also will need to wear sunglasses when you go outside or into a brightly lit room.