The application of fluorescent dye, typically fluorescein, to the surface of the eye is primarily for diagnostic purposes to detect corneal or conjunctival damage, assess tear film abnormalities, and aid in contact lens fitting.
Here's a breakdown of the process and its applications:
How Fluorescein is Applied
- Fluorescein paper strips: The most common method involves a sterile paper strip impregnated with fluorescein dye.
- Moistening the strip: The tip of the strip is moistened with sterile saline solution.
- Application to the eye: The moistened tip is gently touched to the conjunctiva (the lining of the inner eyelid) or the inferior fornix (the space between the lower eyelid and the eyeball).
- Blinking spreads the dye: The patient blinks a few times to distribute the dye evenly across the surface of the eye.
Why Fluorescein is Used
Fluorescein stains damaged areas of the cornea or conjunctiva, making them visible under a cobalt blue light. This allows doctors to:
- Detect corneal abrasions and ulcers: Breaks in the corneal surface will take up the dye and appear bright green.
- Identify foreign bodies: Fluorescein can highlight the presence of a foreign object on the eye's surface.
- Assess tear film: The tear film's stability and drainage can be evaluated using fluorescein. Breaks in the tear film are easily visualized.
- Evaluate contact lens fit: Fluorescein is used to assess the fit of contact lenses, ensuring proper tear exchange and preventing corneal hypoxia.
- Diagnose corneal infections: Certain infections, such as herpes simplex keratitis, have characteristic staining patterns.
- Evaluate for glaucoma: In Goldmann applanation tonometry, fluorescein is used to visualize the mires (small circles) when measuring intraocular pressure. This is a standard test for glaucoma screening and monitoring.
Examples of Applications
- A patient complaining of a painful, scratchy eye may have a corneal abrasion that can be easily visualized with fluorescein staining.
- A patient with dry eye syndrome may exhibit rapid tear break-up time when assessed with fluorescein.
- During a contact lens fitting, fluorescein can reveal areas of excessive or insufficient lens bearing on the cornea.
In summary, applying fluorescent dye to the eye's surface is a vital diagnostic tool in ophthalmology and optometry, enabling the detection of various ocular surface abnormalities and aiding in the management of eye conditions.
