Fluorescein eye stain is a commonly used diagnostic tool in ophthalmology. It helps eye care professionals examine the eye’s surface to identify various conditions. This temporary dye assists in revealing issues not visible during a routine eye examination. Its application is a routine part of many eye health assessments.
The Science of Fluorescein
Fluorescein is a fluorescent dye that appears dark orange or yellow when applied to the eye. Under a cobalt blue light, typically from a slit lamp, the dye absorbs the blue light and re-emits it as a bright yellow-green glow.
Fluorescein adheres to areas where the outer layer of cells on the cornea, known as the epithelium, is damaged or absent. Healthy corneal tissue resists the dye’s penetration. Compromised areas, such as abrasions, ulcers, or foreign bodies, allow the dye to enter and stain the underlying corneal tissue, making the affected regions visible.
How Long Fluorescein Stains the Eye
The diagnostic effect of fluorescein on the eye’s surface is brief. Once applied, the dye typically remains diagnostically useful for only a few minutes, usually 5 to 15 minutes. This rapid clearance is due to the eye’s natural tear production and blinking, which dilute and wash away the dye.
Several factors influence how long the stain is visible and diagnostically effective. The quality and volume of an individual’s tear film play a role; eyes with robust tear production will clear the dye more quickly. A higher blinking rate also contributes to faster dilution. Additionally, the amount and concentration of dye initially applied can affect its persistence on the ocular surface.
What to Expect After Staining
Following fluorescein application, individuals may experience temporary effects. A slight blurriness in vision is common immediately after the dye is introduced. This can be accompanied by increased tear production as the eye clears the substance.
The dye may cause tears to appear yellow or orange, and this color might be visible on the skin around the eyes if tears run down the face. While the stain on the cornea clears quickly, residual yellowing of tears or eyelids might be noticeable for up to 30 minutes to an hour. The dye is harmlessly eliminated from the body.
Safety and Important Considerations
Fluorescein is generally safe and widely used in eye examinations. Most individuals experience no adverse effects. Rarely, a mild, temporary stinging or scratchy sensation may occur when the dye is first applied.
Very rarely, an individual might experience an allergic reaction, which could manifest as hives or itching. If any severe reactions occur, seeking medical attention is advisable. For contact lens wearers, it is important to remove lenses before the dye is applied, as soft lenses can absorb and become stained by fluorescein. Lenses should not be reinserted immediately after the test; it is often recommended to use fresh lenses or thoroughly clean existing ones after the dye has fully cleared to prevent staining.