The slit-lamp examination looks at structures that are at the front of the eye.

Biomicroscopy

The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused to shine in a thin beam.

You will sit in a chair with the instrument placed in front of you. You will be asked to rest your chin and forehead on a support to keep your head steady.

The health care provider will examine your eyes, especially the eyelids, cornea, conjunctiva, sclera, and iris. Often a yellow dye (fluorescein) is used to help examine the cornea and tear layer. The dye is either added as a drop, or the health care provider may touch a fine strip of paper stained with the dye to the white of your eye. The dye rinses out of the eye with tears as you blink.

Next, drops may be placed in your eyes to widen (dilate) your pupils. The drops take about 15 to 20 minutes to work. The slit-lamp examination is then repeated using another small lens held close to the eye, so the back of the eye can be examined.

No special preparation is necessary for this test.

Your eyes will be sensitive to light for a few hours after the exam if dilating drops are used.

This test is used to examine the:

• Conjunctiva
• Cornea
• Eyelids
• Iris
• Lens
• Sclera

Structures in the eye are found to be normal.

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

• Cataract
• Corneal injury
• Dry eye syndrome
• Macular degeneration
• Retinal detachment
• Retinal vessel occlusion
• Retinitis pigmentosa
• Uveitis

This list does not include all possible diseases of the eye.

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

American Academy of Ophthalmology Preferred Practice Patterns Committee. Preferred Practice Pattern Guidelines. Comprehensive Adult Medical Eye Evaluation. Available at http://one.aao.org/CE/PracticeGuidelines/PPP_Content.aspx?cid=64e9df91-dd10-4317-8142-6a87eee7f517. Accessed February 26, 2013.

Colenbrander A. Principles of ophthalmoscopy. In: Tasman W, Jaeger EA, eds. Duane's Ophthalmology. 2013 ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2012:vol 1, chap 63.

Fellman RL, Spaeth GL. Gonioscopy. In: Tasman W, Jaeger EA, eds. Duane's Ophthalmology. 2013 ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2012:vol 3, chap 44.

Miller D, Thall EH, Atebara NH. Ophthalmic instrumentation. In: Yanoff M, Duker JS, eds. Ophthalmology. 3rd ed. Philadelphia, PA: Elsevier Mosby; 2008:chap 2.10.