What Is a Fluorescein Eye Stain Test?
A fluorescein eye stain test is usually ordered if your doctor suspects you have damage on your cornea or foreign objects in your eye. If you wear contact lenses, your doctor might do this test to see whether the contacts are damaging your cornea.
During the test, a dark orange dye called fluorescein is placed onto the outer surface of your eye. Based on the staining, your doctor can identify any problems with your cornea and diagnose certain conditions.
Your doctor may recommend a fluorescein eye stain test if they suspect you have abrasions, or scratches, on your cornea.
The cornea is a clear surface that covers your outer eye. It’s made up of cells and proteins. Unlike most of your body’s other tissues, the cornea contains no blood vessels. It’s protected and nourished by lubrication such as tears.
It has two main functions: to protect your eye from harmful irritants such as dust and germs, and to direct light as it enters your 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 your doctor 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 irritating your corneas or causing any damage.
Your ophthalmologist (eye doctor) will use either a small eyedropper or piece of blotting paper to place the dye into your eye. They’ll ask you to blink several times to allow the dye to spread over 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, the dye will feel like normal liquid on the eye and will no longer be uncomfortable. Your eye surface may have a light yellow appearance.
Your ophthalmologist will then shine a cobalt-blue light onto your eye through a tool made for examining eyes. This tool is called a slit-lamp or ophthalmoscope. The combination of this light and the dye will highlight any abnormalities or abrasions on the cornea. From this, your ophthalmologist can determine the location of any problems and evaluate the level of damage.
If your eye is healthy and your cornea is undamaged, the dye will appear smooth across the entire surface of your eye.
Corneal abrasions or foreign particles will cause abnormal results. These may be a result of:
- trauma to your eye, such as from a fingernail, make-up brush, or other object
- dust, ash, or dirt that has blown into your eye
- a chemical burn
- rubbing your eyes too roughly
- old or improperly cleaned or fitted contact lenses
- any medical condition or situation where your eye is open for a long time, which can dry out the cornea
- the presence of foreign bodies, such as an eyelash
In some cases, the damage could be caused by abnormal tear production, or dry eye. With this condition, you have insufficient tears to nourish and protect the eye. This can lead to inflammation of the cornea. Your test may also reveal a blocked tear duct.
This test is risk-free. The fluorescein dye may stain for a few days if it touches the skin around your eye.
In general, there’s nothing you need to do to prepare for this test. If you wear contact lens, you’ll be asked to take them out beforehand.
After the test, your doctor will use the results to diagnosis any problems you’re having with your eyes. They’ll 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 your eye
- using prescription eye drops or ointment, usually an antibiotic to prevent an infection from developing
- using over-the-counter lubrication tear drops
- 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 to three days. If your injury has penetrated the surface of your eye, healing will take longer, depending on the cause, size, and nature of your injury.