Fluorescein Sodium (Bausch + Lomb)

What Is Fluorescein Sodium and What Is It Used For?

Fluorescein sodium (also known by the brand names Fluoresceinnatrium Bausch + Lomb and Fluorescite) is an ophthalmic diagnostic agent that belongs to the class of fluorescent dyes used extensively in clinical ophthalmology. The active substance is fluorescein, a synthetic organic compound that produces intense green-yellow fluorescence when exposed to cobalt blue light at a wavelength of approximately 485 nanometres, with peak emission at 530 nanometres.

When applied topically to the eye, fluorescein sodium selectively stains areas where the corneal or conjunctival epithelium has been disrupted or damaged. Intact, healthy epithelium does not absorb the dye, which means that areas of injury — such as abrasions, ulcers, dendritic lesions from herpes simplex, or foreign body tracks — appear as brightly fluorescent green patches when examined under blue light with a slit lamp. This contrast makes fluorescein staining one of the most fundamental and widely used diagnostic techniques in eye care.

Clinical Uses of Fluorescein Sodium

Fluorescein sodium eye drops are used in several important clinical applications:

• Corneal and conjunctival injury detection: The primary use of fluorescein is to identify epithelial defects on the cornea and conjunctiva. This includes corneal abrasions from trauma, contact lens-related damage, chemical burns, and infection-related ulceration. The dye highlights the exact location and extent of the injury, guiding treatment decisions.
• Rigid contact lens fitting: During the fitting of rigid gas-permeable (RGP) contact lenses, fluorescein is instilled into the tear film to assess the lens-cornea relationship. The fluorescence pattern reveals areas of contact, clearance, and edge lift, allowing the practitioner to optimise lens fit and prevent corneal damage.
• Seidel test (aqueous humor leak detection): When a corneal perforation is suspected, concentrated fluorescein is applied to the corneal surface. If the aqueous humor is leaking through a wound, it dilutes the fluorescein in a characteristic streaming pattern visible under blue light, confirming the perforation and indicating the need for surgical repair.
• Tear duct patency assessment: Fluorescein dye is instilled into the eye and the nasolacrimal drainage system is assessed over several minutes. If the dye appears in the nasal cavity or throat, it indicates a patent (open) tear drainage system. Absence of dye suggests obstruction, which is particularly useful in evaluating infants with tearing problems and adults with epiphora (excessive tearing).

Fluorescein Angiography (Injection Form)

The injectable form of fluorescein sodium (100 mg/ml) is used for fluorescein angiography (FA), a specialised imaging procedure that photographs the retinal and choroidal blood vessels. After intravenous injection, fluorescein circulates through the ocular vasculature, and sequential photographs are taken as the dye passes through the arteries, capillaries, and veins of the retina. This procedure is invaluable for diagnosing and monitoring conditions such as diabetic retinopathy, age-related macular degeneration (AMD), retinal vein occlusion, and inflammatory eye diseases.

Fluorescein angiography is always performed by trained ophthalmic specialists in a clinical setting, as the intravenous route carries a higher risk of adverse reactions compared to topical application. The procedure typically takes 10–15 minutes, and patients may notice temporary yellowish discolouration of their skin and urine for 24–48 hours afterwards.

What Should You Know Before Using Fluorescein Sodium?

While fluorescein sodium is considered a very safe diagnostic agent when used as directed, there are important considerations that both patients and healthcare providers should be aware of before its application. Understanding contraindications, precautions, and potential interactions helps ensure safe and effective use.

Contraindications

Fluorescein sodium should not be used if you have a known allergy (hypersensitivity) to fluorescein sodium or any of the other ingredients in the formulation. Although allergic reactions to fluorescein are very rare, individuals with a history of allergic reactions to diagnostic dyes should inform their healthcare provider before the examination. Cross-reactivity with other fluorescent dyes has been reported in extremely rare cases.

If you have previously experienced an allergic or anaphylactic reaction to fluorescein in any formulation (eye drops or injection), the product should not be used again. Your healthcare provider can discuss alternative diagnostic methods if fluorescein is contraindicated.

Warnings and Precautions

Rigid gas-permeable (hard) contact lenses are not affected by fluorescein and can remain in the eye during examination. In fact, fluorescein is specifically used during the fitting process for rigid lenses.

After fluorescein application, patients may experience temporary blurred vision due to the dye in the tear film. This effect typically resolves within 10–15 minutes as the dye is washed away by natural tear production. During this period, patients should exercise caution with activities requiring clear vision.

Healthcare professionals should use single-dose units and apply the dye immediately after opening to minimise the risk of microbial contamination. Multi-dose fluorescein solutions have historically been associated with a risk of bacterial contamination, particularly with Pseudomonas aeruginosa, which is why single-dose preservative-free formulations are now preferred in clinical practice.

Pregnancy and Breastfeeding

Fluorescein sodium does cross the placenta and is excreted in breast milk. However, when used topically on the eye (as drops), systemic absorption is extremely limited, and the amount reaching the bloodstream is negligible. No adverse effects on pregnancy, the developing fetus, or the newborn infant are expected from topical ophthalmic use.

Fluorescein sodium eye drops can generally be used during pregnancy and breastfeeding. However, the intravenous injection form results in significantly higher systemic levels and should be used during pregnancy only when the potential benefits clearly outweigh the risks. Breastfeeding mothers who receive intravenous fluorescein may wish to express and discard breast milk for 24–48 hours after the procedure, although the clinical significance of fluorescein in breast milk is uncertain.

As with all medications during pregnancy and breastfeeding, patients should discuss the benefits and risks with their healthcare provider on an individual basis.

Driving and Operating Machinery

Fluorescein sodium can cause temporary blurred vision after application. Patients should not drive or operate heavy machinery until their vision has returned to normal, which typically occurs within 15–30 minutes after the examination. If the eye examination involves additional procedures such as pupil dilation, the period of impaired vision will be longer, and patients should plan transportation accordingly.

How Does Fluorescein Sodium Interact with Other Drugs?

Because fluorescein sodium is a diagnostic agent rather than a therapeutic drug, it has a very favourable interaction profile. It does not undergo significant systemic metabolism when applied topically to the eye, and the brief duration of exposure further limits the potential for drug interactions. However, there are some clinically relevant considerations.

Tell your healthcare provider about all medications you are currently using, including prescription drugs, over-the-counter products, and eye drops. This helps ensure accurate diagnostic results and safe use.

For the injectable form used in fluorescein angiography, additional considerations apply. Beta-blockers and other cardiovascular medications do not need to be discontinued, but clinicians should be aware of the patient's medication history in case of adverse reactions requiring treatment. Patients taking medications that lower the seizure threshold should be monitored, as very rare cases of seizures have been reported following intravenous fluorescein administration.

What Is the Correct Dosage of Fluorescein Sodium?

Fluorescein sodium is a diagnostic agent that is administered by qualified healthcare professionals in a clinical setting. The dosage and method of administration depend on the specific diagnostic procedure being performed. Patients do not typically self-administer fluorescein sodium.

Eye Drops (Topical Application)

Children

Fluorescein sodium eye drops can be used in children at the same topical dosage as adults (1–2 drops). In paediatric practice, fluorescein is commonly used to evaluate corneal injuries in children, to assess nasolacrimal duct obstruction in infants presenting with persistent tearing, and for contact lens fitting in older children. The single-dose preservative-free formulation is preferred for paediatric use.

Elderly

No dose adjustment is required for elderly patients when using the topical eye drop formulation. Fluorescein is routinely used in older adults for the evaluation of dry eye disease, corneal erosions, and during cataract surgery assessment. For intravenous fluorescein angiography in elderly patients, clinicians should take into account any pre-existing cardiovascular or renal conditions.

Overdose

Given the very small amount of fluorescein contained in single-dose eye drop containers (0.5 ml of 2% solution = 10 mg per unit), significant overdose from topical use is extremely unlikely. If a large amount of fluorescein is accidentally ingested (particularly by a child), seek medical advice. Fluorescein is not considered toxic at the doses contained in ophthalmic preparations, but gastrointestinal symptoms such as nausea and temporary yellow discolouration of skin and urine may occur. Contact your local poison control centre or emergency services if concerned.

What Are the Side Effects of Fluorescein Sodium?

Like all medications, fluorescein sodium can cause side effects, although the vast majority of patients experience no adverse reactions when the topical eye drop formulation is used. It is important to distinguish between the expected pharmacological effects of the dye (temporary discolouration and brief blurring of vision) and true adverse reactions, which are uncommon.

The safety profile of topical fluorescein sodium has been well established through decades of clinical use worldwide. The single-dose preservative-free formulation further reduces the risk of adverse reactions by eliminating preservative-related toxicity and minimising the risk of contamination.

Side Effect Frequency Classification

Topical Eye Drops vs. Intravenous Injection: Risk Comparison

It is important to note that the risk of systemic adverse reactions differs substantially between the topical (eye drops) and intravenous (injection) formulations. When applied as eye drops, systemic absorption of fluorescein is minimal, and serious adverse reactions are extremely rare. The intravenous form, used for fluorescein angiography, results in significantly higher blood levels and carries a somewhat greater risk of systemic reactions.

Studies of intravenous fluorescein angiography report mild adverse effects (nausea, vomiting, skin flushing) in approximately 5–10% of patients. Moderate reactions (urticaria, syncope) occur in about 1% of cases. Severe anaphylactoid reactions are rare, estimated at 1 in 2,000 to 1 in 10,000 procedures, and fatalities are extraordinarily rare (approximately 1 in 220,000 procedures according to large retrospective studies).

Reporting Side Effects

Reporting suspected side effects after a medicine has been authorised is important, as it enables ongoing monitoring of the medicine's benefit-risk balance. Healthcare professionals and patients are encouraged to report any suspected adverse reactions to their national medicines regulatory authority (such as the FDA in the United States, the MHRA in the United Kingdom, or the EMA in the European Union).

How Should You Store Fluorescein Sodium?

Proper storage of fluorescein sodium ensures the product remains sterile, effective, and safe throughout its shelf life. The following guidelines apply to the single-dose container formulation (eye drops):

• Temperature: Store at or below 25°C (77°F). The product should be stored at room temperature and protected from excessive heat. Do not refrigerate unless specifically directed, and never freeze the solution.
• Light protection: Keep the single-dose containers in the original outer carton at all times until ready for use. Fluorescein is a light-sensitive compound, and prolonged exposure to light can degrade the solution and reduce its fluorescent intensity.
• Single-use only: Each single-dose container is intended for one-time use only. Remove the container from its outer pouch, twist off the closure, and apply the drops immediately. Discard any remaining solution after use — do not save for later application.
• Expiry date: Do not use after the expiry date printed on the label and outer carton. The expiry date refers to the last day of the stated month.
• Keep out of reach of children: Store this product where children cannot reach it.

Fluorescein sodium eye drops are supplied as individually packaged single-dose polyethylene containers (0.5 ml each), with 20 units per box. Each single-dose unit is sealed in a protective foil pouch to maintain sterility and protect from light degradation.

Do not dispose of medicines via wastewater or household waste. Return unused or expired products to a pharmacy for proper disposal. This helps protect the environment.

What Does Fluorescein Sodium Contain?

Fluorescein sodium eye drops have a notably simple formulation, containing only the active ingredient and purified water. This minimalist composition is an advantage, as it eliminates the risk of adverse reactions to preservatives, buffers, or other excipients commonly found in multi-dose ophthalmic preparations.

Active Ingredient

Fluorescein sodium 20 mg/ml (2% w/v solution). Fluorescein sodium is the disodium salt of fluorescein, a xanthene dye with the chemical formula C₂₀H₁₀Na₂O₅. It has a molecular weight of 376.27 g/mol and appears as an orange-red powder that dissolves readily in water to produce a strongly fluorescent yellow-green solution. The sodium salt form provides superior water solubility compared to the parent fluorescein compound.

Other Ingredients (Excipients)

Purified water. This is the sole excipient in the formulation. The absence of preservatives such as benzalkonium chloride (BAK), which is commonly used in multi-dose eye drops, makes this single-dose formulation particularly suitable for patients with sensitive eyes, preservative allergies, or those using the product frequently.

Packaging and Appearance

The product is supplied as single-dose containers made of flexible low-density polyethylene. Each container holds 0.5 ml of fluorescein sodium 2% solution. The solution appears as a clear, orange-yellow liquid. Containers are packaged in foil pouches (20 units per box) and should be inspected before use — do not use if the container appears damaged, the solution is cloudy, or particles are visible.