Fluorescein
Diagnostic agents
Diagnostic agents
An orange dye that glows green under blue light. On the eye it shows corneal scratches; injected, it outlines the retinal vessels.
Quick facts
- Group
- Diagnostic agents
- Target
- No receptor: a fluorescent dye (absorbs blue light, emits yellow-green light)
- Used for
- Corneal staining to find abrasions
- Key effects
- Nausea · Mild · Headache
- Monitor
- Hives · The injection site
- ATC
- S01JA01
No doses: the clinician sets them by the current guideline.
Mechanism of action
Fluorescein absorbs blue light and gives off yellow-green light. As an eye drop or paper strip it spreads over the tear film; areas where the corneal epithelium is damaged take up the dye and glow green under a blue light. Injected into a vein, it travels to the retina within seconds, and a fundus camera with a blue flash records the retinal and choroidal vessels (fluorescein angiography), showing leaks and closed vessels.
- Fluorescein absorbs blue light and emits green light
- On the eye: damaged cornea takes up the dye and glows
- In a vein: the dye fills retinal vessels and is photographed
Indications
- Corneal staining to find abrasions and foreign bodies Corneal abrasion and ocular foreign body →
- Corneal surface damage in dry eye Dry eye disease →
- Fluorescein angiography of the retina and iris, for example in diabetic retinopathy Diabetic retinopathy →
Adverse effects
Common
- Yellow skin and bright yellow urine after injection (harmless, temporary)
- Nausea, vomiting and a strong taste after injection
- Mild, brief sting from eye drops; dye can stain skin and clothes
- Headache; pain or phlebitis at the injection site
Contraindications
- Hypersensitivity to fluorescein or another ingredient
- Caution with allergies or asthma (emergency equipment ready)
Key interactions
- Topical anaesthetic drops
- Often combined with fluorescein in the same drop; without an anaesthetic the dye may sting briefly
What is monitored
- Hives, breathing and blood pressure during and after injection
- The injection site, for extravasation
Administration and safety
- Glasses and contact lenses come off before an eye stain test.
- For angiography, a well-placed vein is used; if the dye leaks, the injection is stopped and the area treated conservatively.
- An emergency tray is kept at hand; a negative skin test does not rule out allergy.
Pregnancy and breastfeeding
Animal data are insufficient, so injected fluorescein is used in pregnancy only if clearly needed; it passes into breast milk.
Nursing care
- Ask about earlier reactions to fluorescein, allergies and asthma.
- Explain that skin and urine will look yellow for a while and that this is expected.
- Keep a basin ready for nausea and watch for hives or breathlessness.
- Check the IV site for pain or swelling during the injection.
Pharmacokinetics
- Distribution
- After injection in the arm it reaches the central retinal artery within seconds and spreads into the tissues
- Metabolism
- Converted to fluorescein monoglucuronide
- Elimination
- Mainly by the kidney, essentially gone within 48–72 hours; yellow skin fades in 6–12 hours and yellow urine in 24–36 hours
Test yourself
Think of the answer, then tap the question to see it.
What does a corneal abrasion look like after fluorescein under blue light?
A bright green-stained area where the epithelium is missing.
Which harmless effect should every patient know about after fluorescein angiography?
Yellow skin and bright yellow urine for some hours.
What is the most feared reaction to injected fluorescein?
Anaphylaxis, which is rare but can be fatal.
Connections
← Back to the class: Diagnostic agents
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: DailyMed - FLUORESCEIN injection (DailyMed (U.S. National Library of Medicine), 2026); Fluorescein eye stain: MedlinePlus Medical Encyclopedia (MedlinePlus (U.S. National Library of Medicine), 2026); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
Spotted a mistake?We are always improving for the community. Tell us what is wrong and our team will review it.Report a mistake
Representative model, for educational purposes only.