The slit-lamp examination, another name is Biomicroscopy Test looks at structures in the front of the eye. A doctor shines a bright light into an unconscious patient’s eye to check for brain death. If the pupil constricts, the brain is OK, because, in mammals, the brain controls the pupil. The technique for viewing the endothelium involves using a slightly broadened slit beam and setting up the illumination system and microscope so the angle of incident light is equal to the angle of reflection.
Although gonioscopy is the definitive method for examining the iridocorneal angle, the depth of the anterior chamber depth can be approximated by directing the slit beam toward the corneal periphery at an angle of about 60° and examining the distance between the inner surface of the cornea and the iris
How the Test is Performed
The slit-lamp is a low-power microscope combined with a high-intensity light source that can be focused as 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 an eyedrop. Or the 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.
How to Prepare for the Test
No special preparation is needed for this test.
How the Test will Feel
Your eyes will be sensitive to light for a few hours after the exam if dilating drops are used.
Why the Test is Performed
This test is used to examine the:
- Conjunctiva
- Cornea
- Eyelids
- Iris
- Lens
- Sclera
Normal Results
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:
- Clouding of the lens of the eye ( cataract )
- Injury to the clear tissue (cornea) that covers the front of the eye
- Dry eye syndrome
- Loss of sharp vision due to macular degeneration
- Separation of the light-sensitive membrane (retina) in the back of the eye from its supporting layers ( retinal detachment )
- Blockage in a small artery that carries blood to the retina ( retinal vessel occlusion )
- Damage of the retina ( retinitis pigmentosa )
- Swelling and irritation of the uvea ( uveitis ), the middle layer of the eye
This list does not include all possible diseases of the eye.
Risks
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.
