From the Guidelines
To perform a fluorescein stain on the eye, use a saline-moistened fluorescein strip or topical instillation of a 1% to 2% sodium fluorescein solution, and examine the ocular surface through a biomicroscope using a cobalt blue filter after about 2 minutes, as recommended by the most recent study 1. The procedure involves explaining the process to the patient, having them seated comfortably, and using a fluorescein strip moistened with a drop of sterile saline solution or artificial tears.
- The patient should be asked to look up, and then the lower eyelid should be gently pulled down to touch the moistened strip to the inside of the lower lid, being careful not to touch the cornea directly.
- The patient should blink several times to distribute the dye across the eye surface.
- The room lights should be dimmed, and a cobalt blue light source (from a slit lamp or Wood's lamp) should be used to examine the eye.
- The fluorescein will appear bright green under blue light and will highlight any corneal or conjunctival defects, as the dye pools in areas where the epithelium is damaged, as noted in the study 1. Key points to consider when performing the fluorescein stain include:
- Mild fluorescein staining can be observed in normal eyes and may be more prominent in the morning 1.
- Exposure-zone punctate or blotchy fluorescein staining is observed in dry eye, and staining is more easily visualized on the cornea than on the conjunctiva 1. After the examination, the patient should be instructed that their tears may be orange-tinged for a few hours. This staining technique is valuable for detecting corneal abrasions, foreign bodies, ulcers, or dry eye conditions because fluorescein has an affinity for damaged epithelial cells, making otherwise invisible injuries clearly visible under blue light, as supported by the study 1.
From the Research
Fluorescein Stain Procedure
To perform a fluorescein stain on the eye, the following steps can be considered:
- Instillation of fluorescein dye: The dye can be instilled using a disposable calibrated inoculation loop 2 or a single-dose unit 2.
- Volume of dye: The volume of dye collected by a single-use 1 μl-calibrated inoculation loop was measured to be 1.18 ± 0.12 μl 2.
- Assessment: The staining can be assessed using a slit-lamp examination 3, 2 with cobalt blue light and a yellow barrier filter 2.
- Interpretation: The staining patterns can be used to diagnose diseases and monitor treatment outcomes 4.
Important Considerations
- Technique: A proper technique of dye instillation and assessment is important to recognize the changes that can occur 4.
- Dye properties: Sodium fluorescein (NaF) may be cytotoxic when applied in multiple doses 3.
- Patient comfort: Micro-instillation of fluorescein using an inoculation loop can improve patient tolerance by avoiding excess dye 2.