Fluorescein Sodium Ophthalmic Strips: The Complete Guide for Eye Care Professionals

Fluorescein sodium ophthalmic strips are one of the most widely used diagnostic consumables in eye care. From contact lens fitting to corneal abrasion diagnosis, these small strips deliver rapid, accurate staining that is fundamental to anterior segment examination. This guide covers everything eye care professionals need to know — how they work, their key clinical applications, what to look for when buying, and how to store them correctly.

What Are Fluorescein Sodium Ophthalmic Strips?

Fluorescein sodium (NaFl) ophthalmic strips are single-use, sterile paper strips impregnated with fluorescein sodium dye — a water-soluble, non-toxic, orange-yellow fluorescent compound. When moistened with a drop of saline or the patient’s own tears and touched to the lower conjunctival fornix, the dye disperses across the tear film and fluoresces bright green under blue (cobalt) light, revealing areas of corneal or conjunctival epithelial disruption.

The strip format offers significant advantages over fluorescein drops: they are preservative-free, carry a much lower infection risk, have a long shelf life, and deliver a consistent, controlled dose of dye.

Key Clinical Applications

1. Corneal Abrasion and Ulcer Diagnosis

Fluorescein staining is the gold standard for identifying epithelial defects. Disrupted epithelium absorbs the dye and fluoresces intensely under cobalt blue light, clearly delineating the size and shape of the abrasion or ulcer. This allows precise documentation and monitoring of healing.

2. Dry Eye Assessment

The tear film break-up time (TBUT) test uses fluorescein to measure the stability of the precorneal tear film. After instillation, the patient is instructed to blink and then hold their eyes open while the examiner counts the seconds until the first dark spot or streak appears in the fluorescein-stained tear film under cobalt blue illumination. A TBUT under 10 seconds is considered abnormal.

3. Contact Lens Fitting

Fluorescein is essential for evaluating rigid gas-permeable (RGP) contact lens fit. Under blue light, the distribution of dye beneath the lens reveals the fitting relationship — alignment, central clearance, edge lift, and areas of bearing — allowing precise lens parameter adjustments.

4. Lacrimal System Patency (Jones Test)

The Jones I and Jones II tests use fluorescein to assess the patency and drainage function of the nasolacrimal duct system. Fluorescein instilled into the conjunctival sac should appear at the nose or throat within a set time if drainage is functional.

5. Applanation Tonometry

Fluorescein dye is used in Goldmann applanation tonometry to visualise the two semicircular mires required for accurate intraocular pressure measurement. The cobalt filter on the slit lamp biomicroscope causes the dye to fluoresce, making the mire edges clearly visible.

6. Foreign Body Detection

Fluorescein staining helps identify corneal foreign bodies and the epithelial tracks they leave as they traverse the corneal surface, as well as sub-tarsal foreign bodies that have caused linear epithelial abrasions.

Fluorescein Strip Concentrations: 1mg vs 2mg

Fluorescein strips are available in two standard concentrations:

• 1mg strips — lower dye concentration; preferred for TBUT testing, dry eye assessment, and general anterior segment examination where a lighter stain is beneficial
• 2mg strips — higher concentration; preferred for applanation tonometry where stronger fluorescence improves mire visualisation, and for contact lens fitting where good contrast is needed

Most practice protocols use 1mg strips as the default and reserve 2mg strips specifically for tonometry.

How to Use a Fluorescein Strip Correctly

1. Wash hands thoroughly.
2. Open the sterile strip packaging without contaminating the impregnated tip.
3. Moisten the tip with a single drop of sterile unpreserved saline or allow contact with the tear meniscus at the lower lid margin. Avoid over-wetting — excess dye causes pooling that obscures fine detail.
4. Ask the patient to look up and gently touch the moistened tip to the lower conjunctival fornix (not the cornea directly).
5. Ask the patient to blink once to distribute the dye.
6. Examine under cobalt blue illumination using a Burton lamp or slit lamp with the cobalt blue (B/B) filter.
7. Discard the strip immediately after use — never re-use.

Storage and Shelf Life

Fluorescein sodium strips should be stored at room temperature, away from direct light and moisture. Properly stored strips maintain potency for the duration of the manufacturer’s stated expiry date — typically 2–3 years from manufacture. SciMed stocks strips with a 2030 expiry, making them well suited for bulk clinical purchasing.

Do not store strips in humid environments such as open trays near sinks. Once opened, use immediately and discard — partial packs should not be left exposed.

Buying Fluorescein Strips in Bulk

High-volume practices and clinics benefit significantly from bulk purchasing. Each box contains 100 individually wrapped sterile strips. Bulk ordering reduces per-strip cost and ensures continuity of supply for busy departments.

At SciMed Store, we supply USP-grade 1mg fluorescein sodium ophthalmic strips in boxes of 100, with expiry 2030. Orders ship from the USA with same-day dispatch on orders placed before 2PM PST.

Frequently Asked Questions

Are fluorescein strips safe?

Yes. Fluorescein sodium is non-toxic, non-irritating, and has no systemic effects when used topically in the small quantities delivered by a strip. It does not penetrate an intact corneal epithelium — it only stains disrupted epithelium.

Can fluorescein strips be used with contact lenses in situ?

Soft contact lenses should be removed before fluorescein use as the dye permanently stains hydrophilic lens materials. RGP lenses can remain in place for fitting assessments. Advise patients not to reinsert soft lenses for at least 1 hour after instillation.

What is the difference between fluorescein strips and fluorescein drops?

Strips are preservative-free, single-use, and lower contamination risk. Drops (particularly multi-dose bottles) contain preservatives that can cause epithelial toxicity with repeated use. For routine clinical use, strips are strongly preferred.

Do I need a prescription to buy fluorescein strips?

No prescription is required for professional purchase. They are classified as a diagnostic consumable, not a prescription medicine.

Disclaimer: This article is for professional reference purposes. Always follow your clinical protocols and manufacturer instructions for ophthalmic diagnostic procedures.