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Friday, 24 February 2012

Corneal Abrasion Test


Fluorescent eye test
Image source: www.nlm.nih.gov


Fluorescein eye stain
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 outer surface of the eye.

How the Test is Performed
A piece of blotting paper containing the dye will be touched to the surface of your eye. You will be asked to blink. Blinking spreads the dye around 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.)

A blue light is then directed 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 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 identifying 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.

Normal Results
If the test result is normal, the dye remains in the tear film on the surface of the eye and does not adhere to the eye itself.

Note: Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

What Abnormal Results Mean
  • Abnormal tear production (dry eye)
  • Corneal abrasion (a scratch on the surface of the cornea)
  • Foreign bodies, such as eyelashes or dust (see eye - foreign object in)
  • Infection
  • Injury or trauma
  • Severe dry eye associated with arthritis (keratoconjunctivitis sicca)

Risks
If the fluorescein touches the skin surface, there may be a slight, brief, discoloration.

Considerations
This test is very useful for detecting injuries or abnormalities on the surface of the cornea.

References
  • Knoop KJ, Dennis WR, Hedges JR. Ophthalmologic procedures. In: Roberts JR, Hedges JR, eds. Clinical Procedures in Emergency Medicine. 4th ed. Philadelphia, Pa: Saunders Elsevier; 2004: chap 64.
  • Hurwitz JJ. The lacrimal drainage system. In: Yanoff M, Duker JS, Augsburger JJ, Azar DT, eds. Ophthalmology. 2nd ed. Philadelphia, Pa: Mosby Elsevier; 2004: chap 98.

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