Fluorescein Staining in Keratitis Diagnosis
Yes, keratitis will appear with fluorescein staining—fluorescein is a standard diagnostic tool that highlights epithelial defects and corneal damage characteristic of keratitis, making it essential for diagnosis and evaluation.
How Fluorescein Reveals Keratitis
Fluorescein staining is routinely performed during slit-lamp biomicroscopy to detect epithelial defects, which are typically present in bacterial keratitis. 1 The dye works by penetrating areas where corneal epithelial intercellular junctions are disrupted, causing these damaged areas to fluoresce bright green under cobalt blue light. 2
Key Diagnostic Features Revealed by Fluorescein
Epithelial defects are the hallmark finding—fluorescein will pool in areas of corneal ulceration and epithelial loss that characterize infectious keratitis 1
Corneal infiltrates associated with bacterial keratitis typically show an overlying epithelial defect that stains positively with fluorescein 1
The staining helps differentiate true epithelial damage from simple pooling of dye in areas of corneal thinning with intact epithelium—pooling can be wicked away with a cotton swab or irrigation, whereas true epithelial defects will retain the stain 1
Clinical Application in Keratitis Evaluation
Fluorescein staining should be performed as part of the standard slit-lamp examination when keratitis is suspected. 1 The American Academy of Ophthalmology recommends fluorescein for corneal epithelial defect visualization and is FDA-approved for disclosing corneal injury. 2, 3
Proper Technique
Apply fluorescein using a saline-moistened strip to the inferior tarsal conjunctiva, avoiding fluorescein-anesthetic combination drops as anesthetics may affect results 2, 4
Examine the ocular surface through a biomicroscope using a cobalt blue filter 2
Wait approximately 2 minutes after application for optimal visualization, and consider using a yellow filter in conjunction with cobalt blue light 2
Additional Diagnostic Information
Beyond simply detecting epithelial defects, fluorescein staining provides information about:
Dendrites or pseudodendrites that may suggest viral etiology 1
Foreign bodies that may be the source of infection 1
Loose or exposed sutures in post-surgical cases 1
Punctate keratopathy patterns that help characterize the type and severity of corneal involvement 1
Important Clinical Caveats
A critical pitfall is distinguishing true epithelial staining from pooling of fluorescein in areas of stromal thinning with intact epithelium. 1 This is particularly important in keratitis cases with significant stromal involvement or melting, where pooling may create a false impression of more extensive epithelial damage.
- Pooling can be removed by wicking with a cotton swab or irrigating the cornea, whereas true epithelial defects will continue to stain 1
Rare exceptions exist: One case report documented "negative fluorescein staining" as an early sign of Acanthamoeba keratitis due to ridge-like epithelial irregularity, though this represents an atypical presentation. 5
Role in Management Decisions
The presence and characteristics of fluorescein staining help determine the need for cultures and smears. Smears and cultures are specifically recommended when there is a central, large corneal infiltrate (within 3 mm of corneal center and ≥2 mm in size) with associated epithelial defect. 1
Fluorescein staining should be performed before instillation of any other eyedrops to avoid false results, and eyelid manipulation should be avoided before evaluation. 2