During a fluorescein eye stain test, a dark orange dye (fluorescein) is placed onto the outer surface of your eye, called the cornea. A blue light is then shone onto the eye. The dye will show any scratches, tears or foreign particles on your eye as a green color under the light.
Based on the staining, your doctor can identify any problems with your cornea or diagnosis certain conditions.
This test is usually ordered if your doctor suspects you have damage on your cornea or foreign objects in your eye. If you wear contact lens, your doctor might do this test to see whether the contacts are damaging your cornea.
You doctor may recommend a fluorescein eye stain test if he or she suspects you have abrasions, or scratches, on your cornea.
The cornea is a clear surface that covers your outer eye. It is made up of cells and proteins. Unlike most of your body’s other tissues, the cornea contains no blood vessels. It is protected and nourished by tears.
It has two main functions—to protect the eye from dust, germs, and other harmful irritants; and to permit and direct light as it enters the eye.
The cornea is highly sensitive. If it becomes scratched or damaged, new cells quickly cover the injury to prevent infection from occurring. Deeper scratches will take longer to heal and may cause scars. A fluorescein eye stain test can help detect corneal injuries, small foreign objects or particles in the eye, and abnormal tear production.
The test may also help your doctor determine if your contact lenses are irritatingyour corneas.
According to the Developmental Disabilities Health Alliance, this test has a 93 to 97 percent accuracy rate for detecting corneal problems.
Your ophthalmologist (eye doctor) will use either a small eyedropper or piece of blotting paper to place dye into your eye. He or she will ask you to blink several times to allow the dye to completely cover the surface of the cornea. Blinking spreads the dye throughout your tear film—the wet surface of your eyeball that lubricates and protects the eye. The tear film is made up of water, oil, and mucus.
You may feel a slight stinging sensation when the dye is first applied. After a few moments though, the dye will feel like normal liquid on the eye and will no longer be uncomfortable.
The doctor will then shine a cobalt-blue light onto your eye. The combination of this light and the dye will make any abnormalities or abrasions on the cornea appear green. From this, your ophthalmologist will be able to determine the location of any problems and evaluate the level of damage.
If your eye is healthy and the cornea is undamaged, the dye will remain in the film on the surface of your eye and not cause areas to turn green.
Abnormal results from this test may be caused by corneal abrasions, or scratches on the surface of the eye. These abrasions may be a result of:
- a poke in the eye from a fingernail, make-up brush, or other object
- dust, ash, or dirt that has blown into the eye
- a chemical burn
- rubbing your eyes too roughly
- dirty, old, or poorly-fitting contact lenses
- not protecting the eyes during general anesthesia (if they are not closed, the cornea will dry out)
- the presence of foreign bodies, such as an eyelash
- other injuries or trauma to the eye
In some cases, the damage could be caused by abnormal tear production (or dry eye). This is a condition in which there are insufficient tears to nourish and protect the eye, leading to inflammation of the cornea. Your test may also reveal a blocked tear duct.
This test is risk-free. However, the fluorescein dye may stain for a few days if it touches the skin around your eye.
In general, there is nothing you need to do to prepare for this test. If you wear contact lens, you will be asked to take them out beforehand.
After the test, your doctor will use the results to diagnosis any problems you are having with your eyes. He or she will meet with you to discuss the damage discovered on your cornea and plan any necessary treatment.
Treatment options may include:
- removal of the foreign object from the eye
- using prescription eye drops or ointment
- wearing a temporary eye patch or bandage contact lens
- leaving contact lenses out until the cornea has healed
- taking pain medications
If your injury has only affected the surface of your cornea, it should heal in about two days. If the injury has penetrated the surface of the eye, healing will take longer, depending on the cause, size, and nature of the injury.