A corneal ulcer is an open sore on the cornea, the clear outer surface of the eye that covers the iris and pupil. This condition arises from an eye infection, though severe dry eye or other eye disorders can also contribute. To diagnose corneal damage, eye care professionals frequently use a non-invasive procedure known as a fluorescein stain. This test helps reveal injuries or abnormalities on the eye’s surface.
Understanding Fluorescein and Its Purpose
Fluorescein is a fluorescent dye important in ophthalmic diagnostics. It is a water-soluble sodium salt that responds to blue light and fluoresces as a bright green. This dye has a property: it adheres to areas where the corneal epithelium, the outermost protective layer, is damaged or absent, but it does not stain healthy, intact cells. This occurs because when the corneal epithelium is compromised, the tight junctions between cells lose their integrity, allowing the fluorescein to seep into the injured areas.
This characteristic makes fluorescein effective for detecting various corneal issues. It is used to identify conditions such as corneal abrasions (superficial scratches) and corneal ulcers (deeper tissue loss). The dye also helps locate foreign bodies embedded in the cornea. When fluorescein is applied, it is viewed with a cobalt blue filter, which enhances the dye’s fluorescence.
The Examination: What to Expect
The fluorescein stain examination is performed in an eye care professional’s office. It begins with applying a small amount of fluorescein dye to the eye. This can be done using a moistened paper strip or a liquid drop, sometimes combined with a local anesthetic to reduce stinging.
After application, the patient blinks several times to spread the dye evenly across the tear film, the wet, protective layer covering the cornea. An eye care professional then uses a slit lamp or ophthalmoscope equipped with a cobalt blue filter to observe the eye. This combination of blue light and fluorescein causes damaged corneal areas to highlight with a greenish tint. The procedure is quick, taking only minutes, and is painless and safe.
Interpreting the Stain’s Signals
When observed under the cobalt blue light, a positive fluorescein stain appears as bright green or yellow-green areas on the cornea. These glowing areas indicate regions where the superficial layer of the cornea, the epithelium, is damaged or missing. The pattern, location, and extent of this staining provide valuable diagnostic clues about specific eye conditions.
For instance, corneal ulcers typically present as distinct, often round or irregular, intensely stained areas, signifying significant tissue loss. Corneal abrasions, which are superficial injuries, appear as brightly stained scratches or linear patterns. If a foreign body is present, the stain might pool around the object embedded in the cornea.
Punctate, or small dot-like, staining scattered across the cornea can indicate widespread superficial damage often associated with dry eye syndrome. A unique dendritic (tree-branch-like) pattern of staining is characteristic of herpetic keratitis, an infection caused by the herpes simplex virus. These varied patterns help the eye care professional pinpoint the specific nature of the corneal issue.
Immediate Steps After Stain Examination
The fluorescein stain serves as a diagnostic tool, and its results directly inform the subsequent steps in patient care. Once the eye care professional has interpreted the staining patterns and made a diagnosis, they will discuss the findings with the patient. This discussion includes the identified condition, its potential causes, and the recommended course of action.
Treatment plans vary based on the diagnosis and may involve prescribing specific eye drops, such as antibiotics to prevent infection, antivirals for viral conditions, or lubricating drops for dry eye. Protective measures, like wearing a temporary eye patch or bandage contact lens, may be suggested to aid healing. Patients may also be advised to temporarily discontinue contact lens wear. Follow-up appointments are often scheduled to monitor healing and adjust treatment as needed, ensuring proper recovery of the corneal surface.