This is a test that uses orange dye (fluorescein) and a blue light to detect foreign bodies in the eye. This test can also detect damage to the cornea. The cornea is the outer surface of the eye.
How the test is performed
A piece of blotting paper containing the dye is touched to the surface of your eye. You are asked to blink. Blinking spreads the dye and coats the tear film covering the surface of the cornea. The tear film contains water, oil, and mucus to protect and lubricate the eye.
The health care provider then shines a blue light at your eye. Any problems on the surface of the cornea will be stained by the dye and appear green under the blue light.
The health care provider can determine the location and likely cause of the cornea problem depending on the size, location, and shape of the staining.
How to prepare for the test
You will need to remove your eyeglasses or contact lenses before the test.
How the test will feel
If eyes are extremely dry, the blotting paper may be slightly scratchy. The dye may cause a mild and brief stinging sensation.
Why the test is performed
This test is useful in finding superficial scratches or other problems with the surface of the cornea. It can also help reveal foreign bodies on the eye surface. It can be used after contacts are prescribed to determine if there is irritation of the surface of the cornea.
If the test result is normal, the dye remains in the tear film on the surface of the eye and does not stick to the eye itself.
If the fluorescein touches the skin surface, there may be a slight, brief, discoloration.
This test is very useful for detecting injuries or abnormalities on the surface of the cornea.
Knoop KJ, Dennis WR, Hedges JR. Ophthalmologic procedures. In: Roberts JR, Hedges JR, eds. Clinical Procedures in Emergency Medicine. 5th ed. Philadelphia, PA: Elsevier Saunders; 2009:chap 63.
Linda J. Vorvick, MD, Medical Director and Director of Didactic Curriculum, MEDEX Northwest Division of Physician Assistant Studies, Department of Family Medicine, UW Medicine, School of Medicine, University of Washington. Also reviewed by A.D.A.M. Health Solutions, Ebix, Inc., Editorial Team: David Zieve, MD, MHA, David R. Eltz, Stephanie Slon, and Nissi Wang.