Fluorescence Sodium (Mechanism of action)
Fluorescein is a synthetic organic compound available as a dark orange/red powder soluble in water and alcohol. Fluorescence is a type of photoluminescence that occurs when susceptible molecules known as fluorophores absorb electromagnetic energy, temporarily exciting them to a higher energy state. As the molecules return to their original energy level, they emit light of a different, usually longer wavelength.
Unlike phosphorescence, which continues to occur after the excitation source is removed, fluorescence requires continuous excitation. Once the excitation source is removed, emission of fluorescence stops almost immediately (10-8 seconds)
Fluorescence occurs naturally in certain compounds and may occasionally be observed in the human eye.
Fluorescein absorbs blue light, with peak excitation occurring at wavelengths between 465-490 nm. The resulting fluorescence occurs at the yellow-green wavelengths of 520 to 530 nm. Dye concentration and pH can affect the intensity of fluorescence. Maximum fluorescence occurs at a pH of 7.4
Fluorescence is detectable in concentrations between 0.1% and 0.0000001%. In broad-spectrum illumination, diluted fluorescein sodium appears bright yellow-green in color. When illuminated with blue light, the yellow-green color intensifies.
The fluorescent properties of this dye have made it useful in a variety of industrial, scientific, military, and medical applications
It was first fluorescent dye used for water tracing purposes.
It has been used as a visible marker for search-and-rescue operations, to track and measure flow dynamics of water sources, map subterranean water courses, track hazardous spill dispersion patterns, identify point sources of pollution, and to detect leaks or obstructions in plumbing and sewage systems.
Fluorescein sodium ophthalmic strips
In ophthalmology, topical application of fluorescein sodium is routinely used for:-
- Applanation tonometry
- As a vital stain in the documentation of ocular surface disorders such as corneal ulcers, abrasions, or other epithelial defects
- Determine tear film breakup time
- Check the fit of contact lenses
- Patency of lacrimal passage ways
- To detect leakage of aqueous humour from corneal or conjunctival wounds using the Seidel Test.
- Three and nine o’clock staining- present parallel to the nasal and temporal limbus and is due to contact lens associated dry eye. Patients may experience mild discomfort.
- Dimple veil staining- is not true staining, but rather pooling of the dye into corneal indentions caused by trapped air bubbles under a poorly fitting rigid gas permeable contact lens. It presents as sharply demarcated, circular patterns of stain on the cornea.
How to use Fluorescein sodium ophthalmic strips?
Uses in Medicine
- Age-related Macular Degeneration
- Hypertensive Retinopathy
- Vascular Occlusions
Dosage and Administration
Complications and adverse reactions
- Extravasation of dye
- Transient nausea
- Laryngeal oedema
- Myocardial infarction
- Cardiac arrest