Corneal Infiltrate
The term for the white area seen over a foreign body or corneal abrasion is a corneal infiltrate (also called a stromal infiltrate). This represents white cell infiltration and edema in the corneal stroma, appearing as a whitish opacity with indistinct edges at the site of injury 1, 2.
Clinical Characteristics
Corneal infiltrates associated with foreign bodies or abrasions typically present with:
- Suppurative stromal infiltrates - particularly those >1 mm in size with indistinct edges
- Surrounding stromal edema and white cell infiltration
- Epithelial defect overlying the infiltrate (typically present)
- Anterior chamber reaction often accompanies the infiltrate 1, 2
The infiltrate appears white or yellowish-white due to the accumulation of inflammatory cells (neutrophils, lymphocytes) responding to the corneal injury or potential infection.
Important Clinical Distinction
Not all white areas indicate infection. The infiltrate may be:
- Infectious - bacterial keratitis requiring urgent antimicrobial therapy
- Sterile inflammatory - immune response to trauma without active infection
- Foreign body reaction - localized inflammation around embedded material
When to Worry
Seek immediate medical attention for infiltrates that are:
- Central location (within 3 mm of corneal center)
- Large size (≥2 mm)
- Associated with significant stromal involvement or melting
- Multiple infiltrates present
- Anterior chamber cells (≥1+)
- History of contact lens wear, especially overnight wear
- High-velocity injury mechanism
These features suggest bacterial keratitis requiring cultures and aggressive topical antibiotic therapy rather than simple observation.
Common Pitfall
Do not confuse fluorescein pooling in areas of corneal thinning with true epithelial staining. Pooled stain can be wicked away with a cotton swab or irrigation, whereas true epithelial defects retain the stain 2. This distinction is critical because pooling may overestimate the severity of the abrasion.